MySQL and MariaDB

Support for the MySQL / MariaDB database.

The following table summarizes current support levels for database release versions.

Supported MySQL / MariaDB versions

Support type

Versions

Fully tested in CI

5.6, 5.7, 8.0 / 10.4, 10.5

Normal support

5.6+ / 10+

Best effort

5.0.2+ / 5.0.2+

DBAPI Support

The following dialect/DBAPI options are available. Please refer to individual DBAPI sections for connect information.

Supported Versions and Features

SQLAlchemy supports MySQL starting with version 5.0.2 through modern releases, as well as all modern versions of MariaDB. See the official MySQL documentation for detailed information about features supported in any given server release.

Changed in version 1.4: minimum MySQL version supported is now 5.0.2.

MariaDB Support

The MariaDB variant of MySQL retains fundamental compatibility with MySQL’s protocols however the development of these two products continues to diverge. Within the realm of SQLAlchemy, the two databases have a small number of syntactical and behavioral differences that SQLAlchemy accommodates automatically. To connect to a MariaDB database, no changes to the database URL are required:

  1. engine = create_engine("mysql+pymysql://user:pass@some_mariadb/dbname?charset=utf8mb4")

Upon first connect, the SQLAlchemy dialect employs a server version detection scheme that determines if the backing database reports as MariaDB. Based on this flag, the dialect can make different choices in those of areas where its behavior must be different.

MariaDB-Only Mode

The dialect also supports an optional “MariaDB-only” mode of connection, which may be useful for the case where an application makes use of MariaDB-specific features and is not compatible with a MySQL database. To use this mode of operation, replace the “mysql” token in the above URL with “mariadb”:

  1. engine = create_engine("mariadb+pymysql://user:pass@some_mariadb/dbname?charset=utf8mb4")

The above engine, upon first connect, will raise an error if the server version detection detects that the backing database is not MariaDB.

When using an engine with "mariadb" as the dialect name, all mysql-specific options that include the name “mysql” in them are now named with “mariadb”. This means options like mysql_engine should be named mariadb_engine, etc. Both “mysql” and “mariadb” options can be used simultaneously for applications that use URLs with both “mysql” and “mariadb” dialects:

  1. my_table = Table(
  2.     "mytable",
  3.     metadata,
  4.     Column("id", Integer, primary_key=True),
  5.     Column("textdata", String(50)),
  6.     mariadb_engine="InnoDB",
  7.     mysql_engine="InnoDB",
  8. )
  10. Index(
  11.     "textdata_ix",
  12.     my_table.c.textdata,
  13.     mysql_prefix="FULLTEXT",
  14.     mariadb_prefix="FULLTEXT",
  15. )

Similar behavior will occur when the above structures are reflected, i.e. the “mariadb” prefix will be present in the option names when the database URL is based on the “mariadb” name.

New in version 1.4: Added “mariadb” dialect name supporting “MariaDB-only mode” for the MySQL dialect.

Connection Timeouts and Disconnects

MySQL / MariaDB feature an automatic connection close behavior, for connections that have been idle for a fixed period of time, defaulting to eight hours. To circumvent having this issue, use the create_engine.pool_recycle option which ensures that a connection will be discarded and replaced with a new one if it has been present in the pool for a fixed number of seconds:

  1. engine = create_engine('mysql+mysqldb://...', pool_recycle=3600)

For more comprehensive disconnect detection of pooled connections, including accommodation of server restarts and network issues, a pre-ping approach may be employed. See Dealing with Disconnects for current approaches.

See also

Dealing with Disconnects - Background on several techniques for dealing with timed out connections as well as database restarts.

CREATE TABLE arguments including Storage Engines

Both MySQL’s and MariaDB’s CREATE TABLE syntax includes a wide array of special options, including ENGINE, CHARSET, MAX_ROWS, ROW_FORMAT, INSERT_METHOD, and many more. To accommodate the rendering of these arguments, specify the form mysql_argument_name="value". For example, to specify a table with ENGINE of InnoDB, CHARSET of utf8mb4, and KEY_BLOCK_SIZE of 1024:

  1. Table('mytable', metadata,
  2.       Column('data', String(32)),
  3.       mysql_engine='InnoDB',
  4.       mysql_charset='utf8mb4',
  5.       mysql_key_block_size="1024"
  6.      )

When supporting MariaDB-Only Mode mode, similar keys against the “mariadb” prefix must be included as well. The values can of course vary independently so that different settings on MySQL vs. MariaDB may be maintained:

  1. # support both "mysql" and "mariadb-only" engine URLs
  3. Table('mytable', metadata,
  4.       Column('data', String(32)),
  6.       mysql_engine='InnoDB',
  7.       mariadb_engine='InnoDB',
  9.       mysql_charset='utf8mb4',
  10.       mariadb_charset='utf8',
  12.       mysql_key_block_size="1024"
  13.       mariadb_key_block_size="1024"
  15.      )

The MySQL / MariaDB dialects will normally transfer any keyword specified as mysql_keyword_name to be rendered as KEYWORD_NAME in the CREATE TABLE statement. A handful of these names will render with a space instead of an underscore; to support this, the MySQL dialect has awareness of these particular names, which include DATA DIRECTORY (e.g. mysql_data_directory), CHARACTER SET (e.g. mysql_character_set) and INDEX DIRECTORY (e.g. mysql_index_directory).

The most common argument is mysql_engine, which refers to the storage engine for the table. Historically, MySQL server installations would default to MyISAM for this value, although newer versions may be defaulting to InnoDB. The InnoDB engine is typically preferred for its support of transactions and foreign keys.

A Table that is created in a MySQL / MariaDB database with a storage engine of MyISAM will be essentially non-transactional, meaning any INSERT/UPDATE/DELETE statement referring to this table will be invoked as autocommit. It also will have no support for foreign key constraints; while the CREATE TABLE statement accepts foreign key options, when using the MyISAM storage engine these arguments are discarded. Reflecting such a table will also produce no foreign key constraint information.

For fully atomic transactions as well as support for foreign key constraints, all participating CREATE TABLE statements must specify a transactional engine, which in the vast majority of cases is InnoDB.

Case Sensitivity and Table Reflection

Both MySQL and MariaDB have inconsistent support for case-sensitive identifier names, basing support on specific details of the underlying operating system. However, it has been observed that no matter what case sensitivity behavior is present, the names of tables in foreign key declarations are always received from the database as all-lower case, making it impossible to accurately reflect a schema where inter-related tables use mixed-case identifier names.

Therefore it is strongly advised that table names be declared as all lower case both within SQLAlchemy as well as on the MySQL / MariaDB database itself, especially if database reflection features are to be used.

Transaction Isolation Level

All MySQL / MariaDB dialects support setting of transaction isolation level both via a dialect-specific parameter create_engine.isolation_level accepted by create_engine(), as well as the Connection.execution_options.isolation_level argument as passed to Connection.execution_options(). This feature works by issuing the command SET SESSION TRANSACTION ISOLATION LEVEL <level> for each new connection. For the special AUTOCOMMIT isolation level, DBAPI-specific techniques are used.

To set isolation level using create_engine():

  1. engine = create_engine(
  2.                 "mysql+mysqldb://scott:tiger@localhost/test",
  3.                 isolation_level="READ UNCOMMITTED"
  4.             )

To set using per-connection execution options:

  1. connection = engine.connect()
  2. connection = connection.execution_options(
  3.     isolation_level="READ COMMITTED"
  4. )

Valid values for isolation_level include:

  • READ COMMITTED

  • READ UNCOMMITTED

  • REPEATABLE READ

  • SERIALIZABLE

  • AUTOCOMMIT

The special AUTOCOMMIT value makes use of the various “autocommit” attributes provided by specific DBAPIs, and is currently supported by MySQLdb, MySQL-Client, MySQL-Connector Python, and PyMySQL. Using it, the database connection will return true for the value of SELECT @@autocommit;.

There are also more options for isolation level configurations, such as “sub-engine” objects linked to a main Engine which each apply different isolation level settings. See the discussion at Setting Transaction Isolation Levels including DBAPI Autocommit for background.

See also

Setting Transaction Isolation Levels including DBAPI Autocommit

AUTO_INCREMENT Behavior

When creating tables, SQLAlchemy will automatically set AUTO_INCREMENT on the first Integer primary key column which is not marked as a foreign key:

  1. >>> t = Table('mytable', metadata,
  2. ...   Column('mytable_id', Integer, primary_key=True)
  3. ... )
  4. >>> t.create()
  5. CREATE TABLE mytable (
  6.         id INTEGER NOT NULL AUTO_INCREMENT,
  7.         PRIMARY KEY (id)
  8. )

You can disable this behavior by passing False to the Column.autoincrement argument of Column. This flag can also be used to enable auto-increment on a secondary column in a multi-column key for some storage engines:

  1. Table('mytable', metadata,
  2.       Column('gid', Integer, primary_key=True, autoincrement=False),
  3.       Column('id', Integer, primary_key=True)
  4.      )

Server Side Cursors

Server-side cursor support is available for the mysqlclient, PyMySQL, mariadbconnector dialects and may also be available in others. This makes use of either the “buffered=True/False” flag if available or by using a class such as MySQLdb.cursors.SSCursor or pymysql.cursors.SSCursor internally.

Server side cursors are enabled on a per-statement basis by using the Connection.execution_options.stream_results connection execution option:

  1. with engine.connect() as conn:
  2.     result = conn.execution_options(stream_results=True).execute(text("select * from table"))

Note that some kinds of SQL statements may not be supported with server side cursors; generally, only SQL statements that return rows should be used with this option.

Deprecated since version 1.4: The dialect-level server_side_cursors flag is deprecated and will be removed in a future release. Please use the Connection.stream_results execution option for unbuffered cursor support.

See also

Using Server Side Cursors (a.k.a. stream results)

Unicode

Charset Selection

Most MySQL / MariaDB DBAPIs offer the option to set the client character set for a connection. This is typically delivered using the charset parameter in the URL, such as:

  1. e = create_engine(
  2.     "mysql+pymysql://scott:tiger@localhost/test?charset=utf8mb4")

This charset is the client character set for the connection. Some MySQL DBAPIs will default this to a value such as latin1, and some will make use of the default-character-set setting in the my.cnf file as well. Documentation for the DBAPI in use should be consulted for specific behavior.

The encoding used for Unicode has traditionally been 'utf8'. However, for MySQL versions 5.5.3 and MariaDB 5.5 on forward, a new MySQL-specific encoding 'utf8mb4' has been introduced, and as of MySQL 8.0 a warning is emitted by the server if plain utf8 is specified within any server-side directives, replaced with utf8mb3. The rationale for this new encoding is due to the fact that MySQL’s legacy utf-8 encoding only supports codepoints up to three bytes instead of four. Therefore, when communicating with a MySQL or MariaDB database that includes codepoints more than three bytes in size, this new charset is preferred, if supported by both the database as well as the client DBAPI, as in:

  1. e = create_engine(
  2.     "mysql+pymysql://scott:tiger@localhost/test?charset=utf8mb4")

All modern DBAPIs should support the utf8mb4 charset.

In order to use utf8mb4 encoding for a schema that was created with legacy utf8, changes to the MySQL/MariaDB schema and/or server configuration may be required.

See also

The utf8mb4 Character Set - in the MySQL documentation

Dealing with Binary Data Warnings and Unicode

MySQL versions 5.6, 5.7 and later (not MariaDB at the time of this writing) now emit a warning when attempting to pass binary data to the database, while a character set encoding is also in place, when the binary data itself is not valid for that encoding:

  1. default.py:509: Warning: (1300, "Invalid utf8mb4 character string:
  2. 'F9876A'")
  3.   cursor.execute(statement, parameters)

This warning is due to the fact that the MySQL client library is attempting to interpret the binary string as a unicode object even if a datatype such as LargeBinary is in use. To resolve this, the SQL statement requires a binary “character set introducer” be present before any non-NULL value that renders like this:

  1. INSERT INTO table (data) VALUES (_binary %s)

These character set introducers are provided by the DBAPI driver, assuming the use of mysqlclient or PyMySQL (both of which are recommended). Add the query string parameter binary_prefix=true to the URL to repair this warning:

  1. # mysqlclient
  2. engine = create_engine(
  3.     "mysql+mysqldb://scott:tiger@localhost/test?charset=utf8mb4&binary_prefix=true")
  5. # PyMySQL
  6. engine = create_engine(
  7.     "mysql+pymysql://scott:tiger@localhost/test?charset=utf8mb4&binary_prefix=true")

The binary_prefix flag may or may not be supported by other MySQL drivers.

SQLAlchemy itself cannot render this _binary prefix reliably, as it does not work with the NULL value, which is valid to be sent as a bound parameter. As the MySQL driver renders parameters directly into the SQL string, it’s the most efficient place for this additional keyword to be passed.

See also

Character set introducers - on the MySQL website

ANSI Quoting Style

MySQL / MariaDB feature two varieties of identifier “quoting style”, one using backticks and the other using quotes, e.g. `some_identifier` vs. "some_identifier". All MySQL dialects detect which version is in use by checking the value of sql_mode when a connection is first established with a particular Engine. This quoting style comes into play when rendering table and column names as well as when reflecting existing database structures. The detection is entirely automatic and no special configuration is needed to use either quoting style.

Changing the sql_mode

MySQL supports operating in multiple Server SQL Modes for both Servers and Clients. To change the sql_mode for a given application, a developer can leverage SQLAlchemy’s Events system.

In the following example, the event system is used to set the sql_mode on the first_connect and connect events:

  1. from sqlalchemy import create_engine, event
  3. eng = create_engine("mysql+mysqldb://scott:tiger@localhost/test", echo='debug')
  5. # `insert=True` will ensure this is the very first listener to run
  6. @event.listens_for(eng, "connect", insert=True)
  7. def connect(dbapi_connection, connection_record):
  8.     cursor = dbapi_connection.cursor()
  9.     cursor.execute("SET sql_mode = 'STRICT_ALL_TABLES'")
  11. conn = eng.connect()

In the example illustrated above, the “connect” event will invoke the “SET” statement on the connection at the moment a particular DBAPI connection is first created for a given Pool, before the connection is made available to the connection pool. Additionally, because the function was registered with insert=True, it will be prepended to the internal list of registered functions.

MySQL / MariaDB SQL Extensions

Many of the MySQL / MariaDB SQL extensions are handled through SQLAlchemy’s generic function and operator support:

  1. table.select(table.c.password==func.md5('plaintext'))
  2. table.select(table.c.username.op('regexp')('^[a-d]'))

And of course any valid SQL statement can be executed as a string as well.

Some limited direct support for MySQL / MariaDB extensions to SQL is currently available.

INSERT/DELETE…RETURNING

The MariaDB dialect supports 10.5+’s INSERT..RETURNING and DELETE..RETURNING (10.0+) syntaxes. INSERT..RETURNING may be used automatically in some cases in order to fetch newly generated identifiers in place of the traditional approach of using cursor.lastrowid, however cursor.lastrowid is currently still preferred for simple single-statement cases for its better performance.

To specify an explicit RETURNING clause, use the _UpdateBase.returning() method on a per-statement basis:

  1. # INSERT..RETURNING
  2. result = connection.execute(
  3.     table.insert().
  4.     values(name='foo').
  5.     returning(table.c.col1, table.c.col2)
  6. )
  7. print(result.all())
  9. # DELETE..RETURNING
  10. result = connection.execute(
  11.     table.delete().
  12.     where(table.c.name=='foo').
  13.     returning(table.c.col1, table.c.col2)
  14. )
  15. print(result.all())

New in version 2.0: Added support for MariaDB RETURNING

INSERT…ON DUPLICATE KEY UPDATE (Upsert)

MySQL / MariaDB allow “upserts” (update or insert) of rows into a table via the ON DUPLICATE KEY UPDATE clause of the INSERT statement. A candidate row will only be inserted if that row does not match an existing primary or unique key in the table; otherwise, an UPDATE will be performed. The statement allows for separate specification of the values to INSERT versus the values for UPDATE.

SQLAlchemy provides ON DUPLICATE KEY UPDATE support via the MySQL-specific insert() function, which provides the generative method Insert.on_duplicate_key_update():

  1. >>> from sqlalchemy.dialects.mysql import insert
  3. >>> insert_stmt = insert(my_table).values(
  4. ...     id='some_existing_id',
  5. ...     data='inserted value')
  7. >>> on_duplicate_key_stmt = insert_stmt.on_duplicate_key_update(
  8. ...     data=insert_stmt.inserted.data,
  9. ...     status='U'
  10. ... )
  11. >>> print(on_duplicate_key_stmt)
  12. INSERT INTO my_table (id, data) VALUES (%s, %s)
  13. ON DUPLICATE KEY UPDATE data = VALUES(data), status = %s

Unlike PostgreSQL’s “ON CONFLICT” phrase, the “ON DUPLICATE KEY UPDATE” phrase will always match on any primary key or unique key, and will always perform an UPDATE if there’s a match; there are no options for it to raise an error or to skip performing an UPDATE.

ON DUPLICATE KEY UPDATE is used to perform an update of the already existing row, using any combination of new values as well as values from the proposed insertion. These values are normally specified using keyword arguments passed to the Insert.on_duplicate_key_update() given column key values (usually the name of the column, unless it specifies Column.key ) as keys and literal or SQL expressions as values:

  1. >>> insert_stmt = insert(my_table).values(
  2. ...          id='some_existing_id',
  3. ...          data='inserted value')
  5. >>> on_duplicate_key_stmt = insert_stmt.on_duplicate_key_update(
  6. ...     data="some data",
  7. ...     updated_at=func.current_timestamp(),
  8. ... )
  10. >>> print(on_duplicate_key_stmt)
  11. INSERT INTO my_table (id, data) VALUES (%s, %s)
  12. ON DUPLICATE KEY UPDATE data = %s, updated_at = CURRENT_TIMESTAMP

In a manner similar to that of UpdateBase.values(), other parameter forms are accepted, including a single dictionary:

  1. >>> on_duplicate_key_stmt = insert_stmt.on_duplicate_key_update(
  2. ...     {"data": "some data", "updated_at": func.current_timestamp()},
  3. ... )

as well as a list of 2-tuples, which will automatically provide a parameter-ordered UPDATE statement in a manner similar to that described at Parameter Ordered Updates. Unlike the Update object, no special flag is needed to specify the intent since the argument form is this context is unambiguous:

  1. >>> on_duplicate_key_stmt = insert_stmt.on_duplicate_key_update(
  2. ...     [
  3. ...         ("data", "some data"),
  4. ...         ("updated_at", func.current_timestamp()),
  5. ...     ]
  6. ... )
  8. >>> print(on_duplicate_key_stmt)
  9. INSERT INTO my_table (id, data) VALUES (%s, %s)
  10. ON DUPLICATE KEY UPDATE data = %s, updated_at = CURRENT_TIMESTAMP

Changed in version 1.3: support for parameter-ordered UPDATE clause within MySQL ON DUPLICATE KEY UPDATE

Warning

The Insert.on_duplicate_key_update() method does not take into account Python-side default UPDATE values or generation functions, e.g. e.g. those specified using Column.onupdate. These values will not be exercised for an ON DUPLICATE KEY style of UPDATE, unless they are manually specified explicitly in the parameters.

In order to refer to the proposed insertion row, the special alias Insert.inserted is available as an attribute on the Insert object; this object is a ColumnCollection which contains all columns of the target table:

  1. >>> stmt = insert(my_table).values(
  2. ...     id='some_id',
  3. ...     data='inserted value',
  4. ...     author='jlh')
  6. >>> do_update_stmt = stmt.on_duplicate_key_update(
  7. ...     data="updated value",
  8. ...     author=stmt.inserted.author
  9. ... )
  11. >>> print(do_update_stmt)
  12. INSERT INTO my_table (id, data, author) VALUES (%s, %s, %s)
  13. ON DUPLICATE KEY UPDATE data = %s, author = VALUES(author)

When rendered, the “inserted” namespace will produce the expression VALUES(<columnname>).

New in version 1.2: Added support for MySQL ON DUPLICATE KEY UPDATE clause

rowcount Support

SQLAlchemy standardizes the DBAPI cursor.rowcount attribute to be the usual definition of “number of rows matched by an UPDATE or DELETE” statement. This is in contradiction to the default setting on most MySQL DBAPI drivers, which is “number of rows actually modified/deleted”. For this reason, the SQLAlchemy MySQL dialects always add the constants.CLIENT.FOUND_ROWS flag, or whatever is equivalent for the target dialect, upon connection. This setting is currently hardcoded.

See also

CursorResult.rowcount

MySQL / MariaDB- Specific Index Options

MySQL and MariaDB-specific extensions to the Index construct are available.

Index Length

MySQL and MariaDB both provide an option to create index entries with a certain length, where “length” refers to the number of characters or bytes in each value which will become part of the index. SQLAlchemy provides this feature via the mysql_length and/or mariadb_length parameters:

  1. Index('my_index', my_table.c.data, mysql_length=10, mariadb_length=10)
  3. Index('a_b_idx', my_table.c.a, my_table.c.b, mysql_length={'a': 4,
  4.                                                            'b': 9})
  6. Index('a_b_idx', my_table.c.a, my_table.c.b, mariadb_length={'a': 4,
  7.                                                            'b': 9})

Prefix lengths are given in characters for nonbinary string types and in bytes for binary string types. The value passed to the keyword argument must be either an integer (and, thus, specify the same prefix length value for all columns of the index) or a dict in which keys are column names and values are prefix length values for corresponding columns. MySQL and MariaDB only allow a length for a column of an index if it is for a CHAR, VARCHAR, TEXT, BINARY, VARBINARY and BLOB.

Index Prefixes

MySQL storage engines permit you to specify an index prefix when creating an index. SQLAlchemy provides this feature via the mysql_prefix parameter on Index:

  1. Index('my_index', my_table.c.data, mysql_prefix='FULLTEXT')

The value passed to the keyword argument will be simply passed through to the underlying CREATE INDEX, so it must be a valid index prefix for your MySQL storage engine.

New in version 1.1.5.

See also

CREATE INDEX - MySQL documentation

Index Types

Some MySQL storage engines permit you to specify an index type when creating an index or primary key constraint. SQLAlchemy provides this feature via the mysql_using parameter on Index:

  1. Index('my_index', my_table.c.data, mysql_using='hash', mariadb_using='hash')

As well as the mysql_using parameter on PrimaryKeyConstraint:

  1. PrimaryKeyConstraint("data", mysql_using='hash', mariadb_using='hash')

The value passed to the keyword argument will be simply passed through to the underlying CREATE INDEX or PRIMARY KEY clause, so it must be a valid index type for your MySQL storage engine.

More information can be found at:

https://dev.mysql.com/doc/refman/5.0/en/create-index.html

https://dev.mysql.com/doc/refman/5.0/en/create-table.html

Index Parsers

CREATE FULLTEXT INDEX in MySQL also supports a “WITH PARSER” option. This is available using the keyword argument mysql_with_parser:

  1. Index(
  2.     'my_index', my_table.c.data,
  3.     mysql_prefix='FULLTEXT', mysql_with_parser="ngram",
  4.     mariadb_prefix='FULLTEXT', mariadb_with_parser="ngram",
  5. )

New in version 1.3.

MySQL / MariaDB Foreign Keys

MySQL and MariaDB’s behavior regarding foreign keys has some important caveats.

Foreign Key Arguments to Avoid

Neither MySQL nor MariaDB support the foreign key arguments “DEFERRABLE”, “INITIALLY”, or “MATCH”. Using the deferrable or initially keyword argument with ForeignKeyConstraint or ForeignKey will have the effect of these keywords being rendered in a DDL expression, which will then raise an error on MySQL or MariaDB. In order to use these keywords on a foreign key while having them ignored on a MySQL / MariaDB backend, use a custom compile rule:

  1. from sqlalchemy.ext.compiler import compiles
  2. from sqlalchemy.schema import ForeignKeyConstraint
  4. @compiles(ForeignKeyConstraint, "mysql", "mariadb")
  5. def process(element, compiler, **kw):
  6.     element.deferrable = element.initially = None
  7.     return compiler.visit_foreign_key_constraint(element, **kw)

The “MATCH” keyword is in fact more insidious, and is explicitly disallowed by SQLAlchemy in conjunction with the MySQL or MariaDB backends. This argument is silently ignored by MySQL / MariaDB, but in addition has the effect of ON UPDATE and ON DELETE options also being ignored by the backend. Therefore MATCH should never be used with the MySQL / MariaDB backends; as is the case with DEFERRABLE and INITIALLY, custom compilation rules can be used to correct a ForeignKeyConstraint at DDL definition time.

Reflection of Foreign Key Constraints

Not all MySQL / MariaDB storage engines support foreign keys. When using the very common MyISAM MySQL storage engine, the information loaded by table reflection will not include foreign keys. For these tables, you may supply a ForeignKeyConstraint at reflection time:

  1. Table('mytable', metadata,
  2.       ForeignKeyConstraint(['other_id'], ['othertable.other_id']),
  3.       autoload_with=engine
  4.      )

See also

CREATE TABLE arguments including Storage Engines

MySQL / MariaDB Unique Constraints and Reflection

SQLAlchemy supports both the Index construct with the flag unique=True, indicating a UNIQUE index, as well as the UniqueConstraint construct, representing a UNIQUE constraint. Both objects/syntaxes are supported by MySQL / MariaDB when emitting DDL to create these constraints. However, MySQL / MariaDB does not have a unique constraint construct that is separate from a unique index; that is, the “UNIQUE” constraint on MySQL / MariaDB is equivalent to creating a “UNIQUE INDEX”.

When reflecting these constructs, the Inspector.get_indexes() and the Inspector.get_unique_constraints() methods will both return an entry for a UNIQUE index in MySQL / MariaDB. However, when performing full table reflection using Table(..., autoload_with=engine), the UniqueConstraint construct is not part of the fully reflected Table construct under any circumstances; this construct is always represented by a Index with the unique=True setting present in the Table.indexes collection.

TIMESTAMP / DATETIME issues

Rendering ON UPDATE CURRENT TIMESTAMP for MySQL / MariaDB’s explicit_defaults_for_timestamp

MySQL / MariaDB have historically expanded the DDL for the TIMESTAMP datatype into the phrase “TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP”, which includes non-standard SQL that automatically updates the column with the current timestamp when an UPDATE occurs, eliminating the usual need to use a trigger in such a case where server-side update changes are desired.

MySQL 5.6 introduced a new flag explicit_defaults_for_timestamp which disables the above behavior, and in MySQL 8 this flag defaults to true, meaning in order to get a MySQL “on update timestamp” without changing this flag, the above DDL must be rendered explicitly. Additionally, the same DDL is valid for use of the DATETIME datatype as well.

SQLAlchemy’s MySQL dialect does not yet have an option to generate MySQL’s “ON UPDATE CURRENT_TIMESTAMP” clause, noting that this is not a general purpose “ON UPDATE” as there is no such syntax in standard SQL. SQLAlchemy’s Column.server_onupdate parameter is currently not related to this special MySQL behavior.

To generate this DDL, make use of the Column.server_default parameter and pass a textual clause that also includes the ON UPDATE clause:

  1. from sqlalchemy import Table, MetaData, Column, Integer, String, TIMESTAMP
  2. from sqlalchemy import text
  4. metadata = MetaData()
  6. mytable = Table(
  7.     "mytable",
  8.     metadata,
  9.     Column('id', Integer, primary_key=True),
  10.     Column('data', String(50)),
  11.     Column(
  12.         'last_updated',
  13.         TIMESTAMP,
  14.         server_default=text("CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP")
  15.     )
  16. )

The same instructions apply to use of the DateTime and DATETIME datatypes:

  1. from sqlalchemy import DateTime
  3. mytable = Table(
  4.     "mytable",
  5.     metadata,
  6.     Column('id', Integer, primary_key=True),
  7.     Column('data', String(50)),
  8.     Column(
  9.         'last_updated',
  10.         DateTime,
  11.         server_default=text("CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP")
  12.     )
  13. )

Even though the Column.server_onupdate feature does not generate this DDL, it still may be desirable to signal to the ORM that this updated value should be fetched. This syntax looks like the following:

  1. from sqlalchemy.schema import FetchedValue
  3. class MyClass(Base):
  4.     __tablename__ = 'mytable'
  6.     id = Column(Integer, primary_key=True)
  7.     data = Column(String(50))
  8.     last_updated = Column(
  9.         TIMESTAMP,
  10.         server_default=text("CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP"),
  11.         server_onupdate=FetchedValue()
  12.     )

TIMESTAMP Columns and NULL

MySQL historically enforces that a column which specifies the TIMESTAMP datatype implicitly includes a default value of CURRENT_TIMESTAMP, even though this is not stated, and additionally sets the column as NOT NULL, the opposite behavior vs. that of all other datatypes:

  1. mysql> CREATE TABLE ts_test (
  2.     -> a INTEGER,
  3.     -> b INTEGER NOT NULL,
  4.     -> c TIMESTAMP,
  5.     -> d TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  6.     -> e TIMESTAMP NULL);
  7. Query OK, 0 rows affected (0.03 sec)
  9. mysql> SHOW CREATE TABLE ts_test;
  10. +---------+-----------------------------------------------------
  11. | Table   | Create Table
  12. +---------+-----------------------------------------------------
  13. | ts_test | CREATE TABLE `ts_test` (
  14.   `a` int(11) DEFAULT NULL,
  15.   `b` int(11) NOT NULL,
  16.   `c` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  17.   `d` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  18.   `e` timestamp NULL DEFAULT NULL
  19. ) ENGINE=MyISAM DEFAULT CHARSET=latin1

Above, we see that an INTEGER column defaults to NULL, unless it is specified with NOT NULL. But when the column is of type TIMESTAMP, an implicit default of CURRENT_TIMESTAMP is generated which also coerces the column to be a NOT NULL, even though we did not specify it as such.

This behavior of MySQL can be changed on the MySQL side using the explicit_defaults_for_timestamp configuration flag introduced in MySQL 5.6. With this server setting enabled, TIMESTAMP columns behave like any other datatype on the MySQL side with regards to defaults and nullability.

However, to accommodate the vast majority of MySQL databases that do not specify this new flag, SQLAlchemy emits the “NULL” specifier explicitly with any TIMESTAMP column that does not specify nullable=False. In order to accommodate newer databases that specify explicit_defaults_for_timestamp, SQLAlchemy also emits NOT NULL for TIMESTAMP columns that do specify nullable=False. The following example illustrates:

  1. from sqlalchemy import MetaData, Integer, Table, Column, text
  2. from sqlalchemy.dialects.mysql import TIMESTAMP
  4. m = MetaData()
  5. t = Table('ts_test', m,
  6.         Column('a', Integer),
  7.         Column('b', Integer, nullable=False),
  8.         Column('c', TIMESTAMP),
  9.         Column('d', TIMESTAMP, nullable=False)
  10.     )
  13. from sqlalchemy import create_engine
  14. e = create_engine("mysql+mysqldb://scott:tiger@localhost/test", echo=True)
  15. m.create_all(e)

output:

  1. CREATE TABLE ts_test (
  2.     a INTEGER,
  3.     b INTEGER NOT NULL,
  4.     c TIMESTAMP NULL,
  5.     d TIMESTAMP NOT NULL
  6. )

Changed in version 1.0.0: - SQLAlchemy now renders NULL or NOT NULL in all cases for TIMESTAMP columns, to accommodate explicit_defaults_for_timestamp. Prior to this version, it will not render “NOT NULL” for a TIMESTAMP column that is nullable=False.

MySQL SQL Constructs

Object NameDescription

match

Produce a MATCH (X, Y) AGAINST (‘TEXT’) clause.

class sqlalchemy.dialects.mysql.match

Produce a MATCH (X, Y) AGAINST ('TEXT') clause.

E.g.:

  1. from sqlalchemy import desc
  2. from sqlalchemy.dialects.mysql import match
  4. match_expr = match(
  5.     users_table.c.firstname,
  6.     users_table.c.lastname,
  7.     against="Firstname Lastname",
  8. )
  10. stmt = (
  11.     select(users_table)
  12.     .where(match_expr.in_boolean_mode())
  13.     .order_by(desc(match_expr))
  14. )

Would produce SQL resembling:

  1. SELECT id, firstname, lastname
  2. FROM user
  3. WHERE MATCH(firstname, lastname) AGAINST (:param_1 IN BOOLEAN MODE)
  4. ORDER BY MATCH(firstname, lastname) AGAINST (:param_2) DESC

The match() function is a standalone version of the ColumnElement.match() method available on all SQL expressions, as when ColumnElement.match() is used, but allows to pass multiple columns

  • Parameters:

    • cols – column expressions to match against

    • against – expression to be compared towards

    • in_boolean_mode – boolean, set “boolean mode” to true

    • in_natural_language_mode – boolean , set “natural language” to true

    • with_query_expansion – boolean, set “query expansion” to true

New in version 1.4.19.

See also

ColumnElement.match()

Members

in_boolean_mode(), in_natural_language_mode(), inherit_cache, with_query_expansion()

Class signature

class sqlalchemy.dialects.mysql.match (sqlalchemy.sql.expression.Generative, sqlalchemy.sql.expression.BinaryExpression)

  • method sqlalchemy.dialects.mysql.match.in_boolean_mode() → Selfmatch

    Apply the “IN BOOLEAN MODE” modifier to the MATCH expression.

    • Returns:

      a new match instance with modifications applied.

  • method sqlalchemy.dialects.mysql.match.in_natural_language_mode() → Selfmatch

    Apply the “IN NATURAL LANGUAGE MODE” modifier to the MATCH expression.

    • Returns:

      a new match instance with modifications applied.

  • attribute sqlalchemy.dialects.mysql.match.inherit_cache: Optional[bool] = True

    Indicate if this HasCacheKey instance should make use of the cache key generation scheme used by its immediate superclass.

    The attribute defaults to None, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value to False, except that a warning is also emitted.

    This flag can be set to True on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.

    See also

    Enabling Caching Support for Custom Constructs - General guideslines for setting the HasCacheKey.inherit_cache attribute for third-party or user defined SQL constructs.

  • method sqlalchemy.dialects.mysql.match.with_query_expansion() → Selfmatch

    Apply the “WITH QUERY EXPANSION” modifier to the MATCH expression.

    • Returns:

      a new match instance with modifications applied.

MySQL Data Types

As with all SQLAlchemy dialects, all UPPERCASE types that are known to be valid with MySQL are importable from the top level dialect:

  1. from sqlalchemy.dialects.mysql import (
  2.     BIGINT,
  3.     BINARY,
  4.     BIT,
  5.     BLOB,
  6.     BOOLEAN,
  7.     CHAR,
  8.     DATE,
  9.     DATETIME,
  10.     DECIMAL,
  11.     DECIMAL,
  12.     DOUBLE,
  13.     ENUM,
  14.     FLOAT,
  15.     INTEGER,
  16.     LONGBLOB,
  17.     LONGTEXT,
  18.     MEDIUMBLOB,
  19.     MEDIUMINT,
  20.     MEDIUMTEXT,
  21.     NCHAR,
  22.     NUMERIC,
  23.     NVARCHAR,
  24.     REAL,
  25.     SET,
  26.     SMALLINT,
  27.     TEXT,
  28.     TIME,
  29.     TIMESTAMP,
  30.     TINYBLOB,
  31.     TINYINT,
  32.     TINYTEXT,
  33.     VARBINARY,
  34.     VARCHAR,
  35.     YEAR,
  36. )

Types which are specific to MySQL, or have MySQL-specific construction arguments, are as follows:

Object NameDescription

BIGINT

MySQL BIGINTEGER type.

BIT

MySQL BIT type.

CHAR

MySQL CHAR type, for fixed-length character data.

DATETIME

MySQL DATETIME type.

DECIMAL

MySQL DECIMAL type.

ENUM

MySQL ENUM type.

FLOAT

MySQL FLOAT type.

INTEGER

MySQL INTEGER type.

JSON

MySQL JSON type.

LONGBLOB

MySQL LONGBLOB type, for binary data up to 2^32 bytes.

LONGTEXT

MySQL LONGTEXT type, for text up to 2^32 characters.

MEDIUMBLOB

MySQL MEDIUMBLOB type, for binary data up to 2^24 bytes.

MEDIUMINT

MySQL MEDIUMINTEGER type.

MEDIUMTEXT

MySQL MEDIUMTEXT type, for text up to 2^24 characters.

NCHAR

MySQL NCHAR type.

NUMERIC

MySQL NUMERIC type.

NVARCHAR

MySQL NVARCHAR type.

REAL

MySQL REAL type.

SET

MySQL SET type.

SMALLINT

MySQL SMALLINTEGER type.

TIME

MySQL TIME type.

TIMESTAMP

MySQL TIMESTAMP type.

TINYBLOB

MySQL TINYBLOB type, for binary data up to 2^8 bytes.

TINYINT

MySQL TINYINT type.

TINYTEXT

MySQL TINYTEXT type, for text up to 2^8 characters.

VARCHAR

MySQL VARCHAR type, for variable-length character data.

YEAR

MySQL YEAR type, for single byte storage of years 1901-2155.

class sqlalchemy.dialects.mysql.BIGINT

MySQL BIGINTEGER type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.BIGINT (sqlalchemy.dialects.mysql.types._IntegerType, sqlalchemy.types.BIGINT)

  • method sqlalchemy.dialects.mysql.BIGINT.__init__(display_width=None, **kw)

    Construct a BIGINTEGER.

    • Parameters:

      • display_width – Optional, maximum display width for this number.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.BINARY

The SQL BINARY type.

Class signature

class sqlalchemy.dialects.mysql.BINARY (sqlalchemy.types._Binary)

class sqlalchemy.dialects.mysql.BIT

MySQL BIT type.

This type is for MySQL 5.0.3 or greater for MyISAM, and 5.0.5 or greater for MyISAM, MEMORY, InnoDB and BDB. For older versions, use a MSTinyInteger() type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.BIT (sqlalchemy.types.TypeEngine)

class sqlalchemy.dialects.mysql.BLOB

The SQL BLOB type.

Class signature

class sqlalchemy.dialects.mysql.BLOB (sqlalchemy.types.LargeBinary)

  • method sqlalchemy.dialects.mysql.BLOB.__init__(length: Optional[int] = None)

    inherited from the sqlalchemy.types.LargeBinary.__init__ method of LargeBinary

    Construct a LargeBinary type.

    • Parameters:

      length – optional, a length for the column for use in DDL statements, for those binary types that accept a length, such as the MySQL BLOB type.

class sqlalchemy.dialects.mysql.BOOLEAN

The SQL BOOLEAN type.

Class signature

class sqlalchemy.dialects.mysql.BOOLEAN (sqlalchemy.types.Boolean)

  • method sqlalchemy.dialects.mysql.BOOLEAN.__init__(create_constraint: bool = False, name: Optional[str] = None, _create_events: bool = True, _adapted_from: Optional[SchemaType] = None)

    inherited from the sqlalchemy.types.Boolean.__init__ method of Boolean

    Construct a Boolean.

    • Parameters:

      • create_constraint –

        defaults to False. If the boolean is generated as an int/smallint, also create a CHECK constraint on the table that ensures 1 or 0 as a value.

        Note

        it is strongly recommended that the CHECK constraint have an explicit name in order to support schema-management concerns. This can be established either by setting the Boolean.name parameter or by setting up an appropriate naming convention; see Configuring Constraint Naming Conventions for background.

        Changed in version 1.4: - this flag now defaults to False, meaning no CHECK constraint is generated for a non-native enumerated type.

      • name – if a CHECK constraint is generated, specify the name of the constraint.

class sqlalchemy.dialects.mysql.CHAR

MySQL CHAR type, for fixed-length character data.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.CHAR (sqlalchemy.dialects.mysql.types._StringType, sqlalchemy.types.CHAR)

  • method sqlalchemy.dialects.mysql.CHAR.__init__(length=None, **kwargs)

    Construct a CHAR.

    • Parameters:

      • length – Maximum data length, in characters.

      • binary – Optional, use the default binary collation for the national character set. This does not affect the type of data stored, use a BINARY type for binary data.

      • collation – Optional, request a particular collation. Must be compatible with the national character set.

class sqlalchemy.dialects.mysql.DATE

The SQL DATE type.

Class signature

class sqlalchemy.dialects.mysql.DATE (sqlalchemy.types.Date)

class sqlalchemy.dialects.mysql.DATETIME

MySQL DATETIME type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.DATETIME (sqlalchemy.types.DATETIME)

  • method sqlalchemy.dialects.mysql.DATETIME.__init__(timezone=False, fsp=None)

    Construct a MySQL DATETIME type.

    • Parameters:

      • timezone – not used by the MySQL dialect.

      • fsp –

        fractional seconds precision value. MySQL 5.6.4 supports storage of fractional seconds; this parameter will be used when emitting DDL for the DATETIME type.

        Note

        DBAPI driver support for fractional seconds may be limited; current support includes MySQL Connector/Python.

class sqlalchemy.dialects.mysql.DECIMAL

MySQL DECIMAL type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.DECIMAL (sqlalchemy.dialects.mysql.types._NumericType, sqlalchemy.types.DECIMAL)

  • method sqlalchemy.dialects.mysql.DECIMAL.__init__(precision=None, scale=None, asdecimal=True, **kw)

    Construct a DECIMAL.

    • Parameters:

      • precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server.

      • scale – The number of digits after the decimal point.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.DOUBLE

MySQL DOUBLE type.

Class signature

class sqlalchemy.dialects.mysql.DOUBLE (sqlalchemy.dialects.mysql.types._FloatType, sqlalchemy.types.DOUBLE)

  • method sqlalchemy.dialects.mysql.DOUBLE.__init__(precision=None, scale=None, asdecimal=True, **kw)

    Construct a DOUBLE.

    Note

    The DOUBLE type by default converts from float to Decimal, using a truncation that defaults to 10 digits. Specify either scale=n or decimal_return_scale=n in order to change this scale, or asdecimal=False to return values directly as Python floating points.

    • Parameters:

      • precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server.

      • scale – The number of digits after the decimal point.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.ENUM

MySQL ENUM type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.ENUM (sqlalchemy.types.NativeForEmulated, sqlalchemy.types.Enum, sqlalchemy.dialects.mysql.types._StringType)

  • method sqlalchemy.dialects.mysql.ENUM.__init__(*enums, **kw)

    Construct an ENUM.

    E.g.:

    1. Column('myenum', ENUM("foo", "bar", "baz"))

    • Parameters:

      • enums –

        The range of valid values for this ENUM. Values in enums are not quoted, they will be escaped and surrounded by single quotes when generating the schema. This object may also be a PEP-435-compliant enumerated type.

      • strict –

        This flag has no effect.

        Changed in version The: MySQL ENUM type as well as the base Enum type now validates all Python data values.

      • charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand.

      • collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand.

      • ascii – Defaults to False: short-hand for the latin1 character set, generates ASCII in schema.

      • unicode – Defaults to False: short-hand for the ucs2 character set, generates UNICODE in schema.

      • binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class sqlalchemy.dialects.mysql.FLOAT

MySQL FLOAT type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.FLOAT (sqlalchemy.dialects.mysql.types._FloatType, sqlalchemy.types.FLOAT)

  • method sqlalchemy.dialects.mysql.FLOAT.__init__(precision=None, scale=None, asdecimal=False, **kw)

    Construct a FLOAT.

    • Parameters:

      • precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server.

      • scale – The number of digits after the decimal point.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.INTEGER

MySQL INTEGER type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.INTEGER (sqlalchemy.dialects.mysql.types._IntegerType, sqlalchemy.types.INTEGER)

  • method sqlalchemy.dialects.mysql.INTEGER.__init__(display_width=None, **kw)

    Construct an INTEGER.

    • Parameters:

      • display_width – Optional, maximum display width for this number.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.JSON

MySQL JSON type.

MySQL supports JSON as of version 5.7. MariaDB supports JSON (as an alias for LONGTEXT) as of version 10.2.

JSON is used automatically whenever the base JSON datatype is used against a MySQL or MariaDB backend.

See also

JSON - main documentation for the generic cross-platform JSON datatype.

The JSON type supports persistence of JSON values as well as the core index operations provided by JSON datatype, by adapting the operations to render the JSON_EXTRACT function at the database level.

New in version 1.1.

Class signature

class sqlalchemy.dialects.mysql.JSON (sqlalchemy.types.JSON)

class sqlalchemy.dialects.mysql.LONGBLOB

MySQL LONGBLOB type, for binary data up to 2^32 bytes.

Class signature

class sqlalchemy.dialects.mysql.LONGBLOB (sqlalchemy.types._Binary)

class sqlalchemy.dialects.mysql.LONGTEXT

MySQL LONGTEXT type, for text up to 2^32 characters.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.LONGTEXT (sqlalchemy.dialects.mysql.types._StringType)

  • method sqlalchemy.dialects.mysql.LONGTEXT.__init__(**kwargs)

    Construct a LONGTEXT.

    • Parameters:

      • charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand.

      • collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand.

      • ascii – Defaults to False: short-hand for the latin1 character set, generates ASCII in schema.

      • unicode – Defaults to False: short-hand for the ucs2 character set, generates UNICODE in schema.

      • national – Optional. If true, use the server’s configured national character set.

      • binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class sqlalchemy.dialects.mysql.MEDIUMBLOB

MySQL MEDIUMBLOB type, for binary data up to 2^24 bytes.

Class signature

class sqlalchemy.dialects.mysql.MEDIUMBLOB (sqlalchemy.types._Binary)

class sqlalchemy.dialects.mysql.MEDIUMINT

MySQL MEDIUMINTEGER type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.MEDIUMINT (sqlalchemy.dialects.mysql.types._IntegerType)

  • method sqlalchemy.dialects.mysql.MEDIUMINT.__init__(display_width=None, **kw)

    Construct a MEDIUMINTEGER

    • Parameters:

      • display_width – Optional, maximum display width for this number.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.MEDIUMTEXT

MySQL MEDIUMTEXT type, for text up to 2^24 characters.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.MEDIUMTEXT (sqlalchemy.dialects.mysql.types._StringType)

  • method sqlalchemy.dialects.mysql.MEDIUMTEXT.__init__(**kwargs)

    Construct a MEDIUMTEXT.

    • Parameters:

      • charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand.

      • collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand.

      • ascii – Defaults to False: short-hand for the latin1 character set, generates ASCII in schema.

      • unicode – Defaults to False: short-hand for the ucs2 character set, generates UNICODE in schema.

      • national – Optional. If true, use the server’s configured national character set.

      • binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class sqlalchemy.dialects.mysql.NCHAR

MySQL NCHAR type.

For fixed-length character data in the server’s configured national character set.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.NCHAR (sqlalchemy.dialects.mysql.types._StringType, sqlalchemy.types.NCHAR)

  • method sqlalchemy.dialects.mysql.NCHAR.__init__(length=None, **kwargs)

    Construct an NCHAR.

    • Parameters:

      • length – Maximum data length, in characters.

      • binary – Optional, use the default binary collation for the national character set. This does not affect the type of data stored, use a BINARY type for binary data.

      • collation – Optional, request a particular collation. Must be compatible with the national character set.

class sqlalchemy.dialects.mysql.NUMERIC

MySQL NUMERIC type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.NUMERIC (sqlalchemy.dialects.mysql.types._NumericType, sqlalchemy.types.NUMERIC)

  • method sqlalchemy.dialects.mysql.NUMERIC.__init__(precision=None, scale=None, asdecimal=True, **kw)

    Construct a NUMERIC.

    • Parameters:

      • precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server.

      • scale – The number of digits after the decimal point.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.NVARCHAR

MySQL NVARCHAR type.

For variable-length character data in the server’s configured national character set.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.NVARCHAR (sqlalchemy.dialects.mysql.types._StringType, sqlalchemy.types.NVARCHAR)

  • method sqlalchemy.dialects.mysql.NVARCHAR.__init__(length=None, **kwargs)

    Construct an NVARCHAR.

    • Parameters:

      • length – Maximum data length, in characters.

      • binary – Optional, use the default binary collation for the national character set. This does not affect the type of data stored, use a BINARY type for binary data.

      • collation – Optional, request a particular collation. Must be compatible with the national character set.

class sqlalchemy.dialects.mysql.REAL

MySQL REAL type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.REAL (sqlalchemy.dialects.mysql.types._FloatType, sqlalchemy.types.REAL)

  • method sqlalchemy.dialects.mysql.REAL.__init__(precision=None, scale=None, asdecimal=True, **kw)

    Construct a REAL.

    Note

    The REAL type by default converts from float to Decimal, using a truncation that defaults to 10 digits. Specify either scale=n or decimal_return_scale=n in order to change this scale, or asdecimal=False to return values directly as Python floating points.

    • Parameters:

      • precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server.

      • scale – The number of digits after the decimal point.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.SET

MySQL SET type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.SET (sqlalchemy.dialects.mysql.types._StringType)

  • method sqlalchemy.dialects.mysql.SET.__init__(*values, **kw)

    Construct a SET.

    E.g.:

    1. Column('myset', SET("foo", "bar", "baz"))

    The list of potential values is required in the case that this set will be used to generate DDL for a table, or if the SET.retrieve_as_bitwise flag is set to True.

    • Parameters:

      • values – The range of valid values for this SET. The values are not quoted, they will be escaped and surrounded by single quotes when generating the schema.

      • convert_unicode – Same flag as that of String.convert_unicode.

      • collation – same as that of String.collation

      • charset – same as that of VARCHAR.charset.

      • ascii – same as that of VARCHAR.ascii.

      • unicode – same as that of VARCHAR.unicode.

      • binary – same as that of VARCHAR.binary.

      • retrieve_as_bitwise –

        if True, the data for the set type will be persisted and selected using an integer value, where a set is coerced into a bitwise mask for persistence. MySQL allows this mode which has the advantage of being able to store values unambiguously, such as the blank string ''. The datatype will appear as the expression col + 0 in a SELECT statement, so that the value is coerced into an integer value in result sets. This flag is required if one wishes to persist a set that can store the blank string '' as a value.

        Warning

        When using SET.retrieve_as_bitwise, it is essential that the list of set values is expressed in the exact same order as exists on the MySQL database.

        New in version 1.0.0.

class sqlalchemy.dialects.mysql.SMALLINT

MySQL SMALLINTEGER type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.SMALLINT (sqlalchemy.dialects.mysql.types._IntegerType, sqlalchemy.types.SMALLINT)

  • method sqlalchemy.dialects.mysql.SMALLINT.__init__(display_width=None, **kw)

    Construct a SMALLINTEGER.

    • Parameters:

      • display_width – Optional, maximum display width for this number.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.TEXT

MySQL TEXT type, for text up to 2^16 characters.

Class signature

class sqlalchemy.dialects.mysql.TEXT (sqlalchemy.dialects.mysql.types._StringType, sqlalchemy.types.TEXT)

  • method sqlalchemy.dialects.mysql.TEXT.__init__(length=None, **kw)

    Construct a TEXT.

    • Parameters:

      • length – Optional, if provided the server may optimize storage by substituting the smallest TEXT type sufficient to store length characters.

      • charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand.

      • collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand.

      • ascii – Defaults to False: short-hand for the latin1 character set, generates ASCII in schema.

      • unicode – Defaults to False: short-hand for the ucs2 character set, generates UNICODE in schema.

      • national – Optional. If true, use the server’s configured national character set.

      • binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class sqlalchemy.dialects.mysql.TIME

MySQL TIME type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.TIME (sqlalchemy.types.TIME)

  • method sqlalchemy.dialects.mysql.TIME.__init__(timezone=False, fsp=None)

    Construct a MySQL TIME type.

    • Parameters:

      • timezone – not used by the MySQL dialect.

      • fsp –

        fractional seconds precision value. MySQL 5.6 supports storage of fractional seconds; this parameter will be used when emitting DDL for the TIME type.

        Note

        DBAPI driver support for fractional seconds may be limited; current support includes MySQL Connector/Python.

class sqlalchemy.dialects.mysql.TIMESTAMP

MySQL TIMESTAMP type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.TIMESTAMP (sqlalchemy.types.TIMESTAMP)

  • method sqlalchemy.dialects.mysql.TIMESTAMP.__init__(timezone=False, fsp=None)

    Construct a MySQL TIMESTAMP type.

    • Parameters:

      • timezone – not used by the MySQL dialect.

      • fsp –

        fractional seconds precision value. MySQL 5.6.4 supports storage of fractional seconds; this parameter will be used when emitting DDL for the TIMESTAMP type.

        Note

        DBAPI driver support for fractional seconds may be limited; current support includes MySQL Connector/Python.

class sqlalchemy.dialects.mysql.TINYBLOB

MySQL TINYBLOB type, for binary data up to 2^8 bytes.

Class signature

class sqlalchemy.dialects.mysql.TINYBLOB (sqlalchemy.types._Binary)

class sqlalchemy.dialects.mysql.TINYINT

MySQL TINYINT type.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.TINYINT (sqlalchemy.dialects.mysql.types._IntegerType)

  • method sqlalchemy.dialects.mysql.TINYINT.__init__(display_width=None, **kw)

    Construct a TINYINT.

    • Parameters:

      • display_width – Optional, maximum display width for this number.

      • unsigned – a boolean, optional.

      • zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class sqlalchemy.dialects.mysql.TINYTEXT

MySQL TINYTEXT type, for text up to 2^8 characters.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.TINYTEXT (sqlalchemy.dialects.mysql.types._StringType)

  • method sqlalchemy.dialects.mysql.TINYTEXT.__init__(**kwargs)

    Construct a TINYTEXT.

    • Parameters:

      • charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand.

      • collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand.

      • ascii – Defaults to False: short-hand for the latin1 character set, generates ASCII in schema.

      • unicode – Defaults to False: short-hand for the ucs2 character set, generates UNICODE in schema.

      • national – Optional. If true, use the server’s configured national character set.

      • binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class sqlalchemy.dialects.mysql.VARBINARY

The SQL VARBINARY type.

Class signature

class sqlalchemy.dialects.mysql.VARBINARY (sqlalchemy.types._Binary)

class sqlalchemy.dialects.mysql.VARCHAR

MySQL VARCHAR type, for variable-length character data.

Members

__init__()

Class signature

class sqlalchemy.dialects.mysql.VARCHAR (sqlalchemy.dialects.mysql.types._StringType, sqlalchemy.types.VARCHAR)

  • method sqlalchemy.dialects.mysql.VARCHAR.__init__(length=None, **kwargs)

    Construct a VARCHAR.

    • Parameters:

      • charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand.

      • collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand.

      • ascii – Defaults to False: short-hand for the latin1 character set, generates ASCII in schema.

      • unicode – Defaults to False: short-hand for the ucs2 character set, generates UNICODE in schema.

      • national – Optional. If true, use the server’s configured national character set.

      • binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class sqlalchemy.dialects.mysql.YEAR

MySQL YEAR type, for single byte storage of years 1901-2155.

Class signature

class sqlalchemy.dialects.mysql.YEAR (sqlalchemy.types.TypeEngine)

MySQL DML Constructs

Object NameDescription

insert(table)

Construct a MySQL/MariaDB-specific variant Insert construct.

Insert

MySQL-specific implementation of INSERT.

function sqlalchemy.dialects.mysql.insert(table)

Construct a MySQL/MariaDB-specific variant Insert construct.

The sqlalchemy.dialects.mysql.insert() function creates a sqlalchemy.dialects.mysql.Insert. This class is based on the dialect-agnostic Insert construct which may be constructed using the insert() function in SQLAlchemy Core.

The Insert construct includes additional methods Insert.on_duplicate_key_update().

class sqlalchemy.dialects.mysql.Insert

MySQL-specific implementation of INSERT.

Adds methods for MySQL-specific syntaxes such as ON DUPLICATE KEY UPDATE.

The Insert object is created using the sqlalchemy.dialects.mysql.insert() function.

New in version 1.2.

Members

inherit_cache, inserted, on_duplicate_key_update()

Class signature

class sqlalchemy.dialects.mysql.Insert (sqlalchemy.sql.expression.Insert)

  • attribute sqlalchemy.dialects.mysql.Insert.inherit_cache: Optional[bool] = False

    Indicate if this HasCacheKey instance should make use of the cache key generation scheme used by its immediate superclass.

    The attribute defaults to None, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value to False, except that a warning is also emitted.

    This flag can be set to True on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.

    See also

    Enabling Caching Support for Custom Constructs - General guideslines for setting the HasCacheKey.inherit_cache attribute for third-party or user defined SQL constructs.

  • attribute sqlalchemy.dialects.mysql.Insert.inserted

    Provide the “inserted” namespace for an ON DUPLICATE KEY UPDATE statement

    MySQL’s ON DUPLICATE KEY UPDATE clause allows reference to the row that would be inserted, via a special function called VALUES(). This attribute provides all columns in this row to be referenceable such that they will render within a VALUES() function inside the ON DUPLICATE KEY UPDATE clause. The attribute is named .inserted so as not to conflict with the existing Insert.values() method.

    Tip

    The Insert.inserted attribute is an instance of ColumnCollection, which provides an interface the same as that of the Table.c collection described at Accessing Tables and Columns. With this collection, ordinary names are accessible like attributes (e.g. stmt.inserted.some_column), but special names and dictionary method names should be accessed using indexed access, such as stmt.inserted["column name"] or stmt.inserted["values"]. See the docstring for ColumnCollection for further examples.

    See also

    INSERT…ON DUPLICATE KEY UPDATE (Upsert) - example of how to use Insert.inserted

  • method sqlalchemy.dialects.mysql.Insert.on_duplicate_key_update(*args, **kw) → SelfInsert

    Specifies the ON DUPLICATE KEY UPDATE clause.

    • Parameters:

      **kw – Column keys linked to UPDATE values. The values may be any SQL expression or supported literal Python values.

    Warning

    This dictionary does not take into account Python-specified default UPDATE values or generation functions, e.g. those specified using Column.onupdate. These values will not be exercised for an ON DUPLICATE KEY UPDATE style of UPDATE, unless values are manually specified here.

    • Parameters:

      *args –

      As an alternative to passing key/value parameters, a dictionary or list of 2-tuples can be passed as a single positional argument.

      Passing a single dictionary is equivalent to the keyword argument form:

      1. insert().on_duplicate_key_update({"name": "some name"})

      Passing a list of 2-tuples indicates that the parameter assignments in the UPDATE clause should be ordered as sent, in a manner similar to that described for the Update construct overall in Parameter Ordered Updates:

      1. insert().on_duplicate_key_update(
      2.     [("name", "some name"), ("value", "some value")])

      Changed in version 1.3: parameters can be specified as a dictionary or list of 2-tuples; the latter form provides for parameter ordering.

    New in version 1.2.

    See also

    INSERT…ON DUPLICATE KEY UPDATE (Upsert)

mysqlclient (fork of MySQL-Python)

Support for the MySQL / MariaDB database via the mysqlclient (maintained fork of MySQL-Python) driver.

DBAPI

Documentation and download information (if applicable) for mysqlclient (maintained fork of MySQL-Python) is available at: https://pypi.org/project/mysqlclient/

Connecting

Connect String:

  1. mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>

Driver Status

The mysqlclient DBAPI is a maintained fork of the MySQL-Python DBAPI that is no longer maintained. mysqlclient supports Python 2 and Python 3 and is very stable.

Unicode

Please see Unicode for current recommendations on unicode handling.

SSL Connections

The mysqlclient and PyMySQL DBAPIs accept an additional dictionary under the key “ssl”, which may be specified using the create_engine.connect_args dictionary:

  1. engine = create_engine(
  2.     "mysql+mysqldb://scott:tiger@192.168.0.134/test",
  3.     connect_args={
  4.         "ssl": {
  5.             "ca": "/home/gord/client-ssl/ca.pem",
  6.             "cert": "/home/gord/client-ssl/client-cert.pem",
  7.             "key": "/home/gord/client-ssl/client-key.pem"
  8.         }
  9.     }
  10. )

For convenience, the following keys may also be specified inline within the URL where they will be interpreted into the “ssl” dictionary automatically: “ssl_ca”, “ssl_cert”, “ssl_key”, “ssl_capath”, “ssl_cipher”, “ssl_check_hostname”. An example is as follows:

  1. connection_uri = (
  2.     "mysql+mysqldb://scott:tiger@192.168.0.134/test"
  3.     "?ssl_ca=/home/gord/client-ssl/ca.pem"
  4.     "&ssl_cert=/home/gord/client-ssl/client-cert.pem"
  5.     "&ssl_key=/home/gord/client-ssl/client-key.pem"
  6. )

See also

SSL Connections in the PyMySQL dialect

Using MySQLdb with Google Cloud SQL

Google Cloud SQL now recommends use of the MySQLdb dialect. Connect using a URL like the following:

  1. mysql+mysqldb://root@/<dbname>?unix_socket=/cloudsql/<projectid>:<instancename>

Server Side Cursors

The mysqldb dialect supports server-side cursors. See Server Side Cursors.

PyMySQL

Support for the MySQL / MariaDB database via the PyMySQL driver.

DBAPI

Documentation and download information (if applicable) for PyMySQL is available at: https://pymysql.readthedocs.io/

Connecting

Connect String:

  1. mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]

Unicode

Please see Unicode for current recommendations on unicode handling.

SSL Connections

The PyMySQL DBAPI accepts the same SSL arguments as that of MySQLdb, described at SSL Connections. See that section for additional examples.

If the server uses an automatically-generated certificate that is self-signed or does not match the host name (as seen from the client), it may also be necessary to indicate ssl_check_hostname=false in PyMySQL:

  1. connection_uri = (
  2.     "mysql+pymysql://scott:tiger@192.168.0.134/test"
  3.     "?ssl_ca=/home/gord/client-ssl/ca.pem"
  4.     "&ssl_cert=/home/gord/client-ssl/client-cert.pem"
  5.     "&ssl_key=/home/gord/client-ssl/client-key.pem"
  6.     "&ssl_check_hostname=false"
  7. )

MySQL-Python Compatibility

The pymysql DBAPI is a pure Python port of the MySQL-python (MySQLdb) driver, and targets 100% compatibility. Most behavioral notes for MySQL-python apply to the pymysql driver as well.

MariaDB-Connector

Support for the MySQL / MariaDB database via the MariaDB Connector/Python driver.

DBAPI

Documentation and download information (if applicable) for MariaDB Connector/Python is available at: https://pypi.org/project/mariadb/

Connecting

Connect String:

  1. mariadb+mariadbconnector://<user>:<password>@<host>[:<port>]/<dbname>

Driver Status

MariaDB Connector/Python enables Python programs to access MariaDB and MySQL databases using an API which is compliant with the Python DB API 2.0 (PEP-249). It is written in C and uses MariaDB Connector/C client library for client server communication.

Note that the default driver for a mariadb:// connection URI continues to be mysqldb. mariadb+mariadbconnector:// is required to use this driver.

MySQL-Connector

Support for the MySQL / MariaDB database via the MySQL Connector/Python driver.

DBAPI

Documentation and download information (if applicable) for MySQL Connector/Python is available at: https://pypi.org/project/mysql-connector-python/

Connecting

Connect String:

  1. mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>

Note

The MySQL Connector/Python DBAPI has had many issues since its release, some of which may remain unresolved, and the mysqlconnector dialect is not tested as part of SQLAlchemy’s continuous integration. The recommended MySQL dialects are mysqlclient and PyMySQL.

asyncmy

Support for the MySQL / MariaDB database via the asyncmy driver.

DBAPI

Documentation and download information (if applicable) for asyncmy is available at: https://github.com/long2ice/asyncmy

Connecting

Connect String:

  1. mysql+asyncmy://user:password@host:port/dbname[?key=value&key=value...]

Note

The asyncmy dialect as of September, 2021 was added to provide MySQL/MariaDB asyncio compatibility given that the aiomysql database driver has become unmaintained, however asyncmy is itself very new.

Using a special asyncio mediation layer, the asyncmy dialect is usable as the backend for the SQLAlchemy asyncio extension package.

This dialect should normally be used only with the create_async_engine() engine creation function:

  1. from sqlalchemy.ext.asyncio import create_async_engine
  2. engine = create_async_engine("mysql+asyncmy://user:pass@hostname/dbname?charset=utf8mb4")

aiomysql

Support for the MySQL / MariaDB database via the aiomysql driver.

DBAPI

Documentation and download information (if applicable) for aiomysql is available at: https://github.com/aio-libs/aiomysql

Connecting

Connect String:

  1. mysql+aiomysql://user:password@host:port/dbname[?key=value&key=value...]

Warning

The aiomysql dialect is not currently tested as part of SQLAlchemy’s continuous integration. As of September, 2021 the driver appears to be unmaintained and no longer functions for Python version 3.10, and additionally depends on a significantly outdated version of PyMySQL. Please refer to the asyncmy dialect for current MySQL/MariaDB asyncio functionality.

The aiomysql dialect is SQLAlchemy’s second Python asyncio dialect.

Using a special asyncio mediation layer, the aiomysql dialect is usable as the backend for the SQLAlchemy asyncio extension package.

This dialect should normally be used only with the create_async_engine() engine creation function:

  1. from sqlalchemy.ext.asyncio import create_async_engine
  2. engine = create_async_engine("mysql+aiomysql://user:pass@hostname/dbname?charset=utf8mb4")

cymysql

Support for the MySQL / MariaDB database via the CyMySQL driver.

DBAPI

Documentation and download information (if applicable) for CyMySQL is available at: https://github.com/nakagami/CyMySQL

Connecting

Connect String:

  1. mysql+cymysql://<username>:<password>@<host>/<dbname>[?<options>]

Note

The CyMySQL dialect is not tested as part of SQLAlchemy’s continuous integration and may have unresolved issues. The recommended MySQL dialects are mysqlclient and PyMySQL.

pyodbc

Support for the MySQL / MariaDB database via the PyODBC driver.

DBAPI

Documentation and download information (if applicable) for PyODBC is available at: https://pypi.org/project/pyodbc/

Connecting

Connect String:

  1. mysql+pyodbc://<username>:<password>@<dsnname>

Note

The PyODBC for MySQL dialect is not tested as part of SQLAlchemy’s continuous integration. The recommended MySQL dialects are mysqlclient and PyMySQL. However, if you want to use the mysql+pyodbc dialect and require full support for utf8mb4 characters (including supplementary characters like emoji) be sure to use a current release of MySQL Connector/ODBC and specify the “ANSI” (not “Unicode”) version of the driver in your DSN or connection string.

Pass through exact pyodbc connection string:

  1. import urllib
  2. connection_string = (
  3.     'DRIVER=MySQL ODBC 8.0 ANSI Driver;'
  4.     'SERVER=localhost;'
  5.     'PORT=3307;'
  6.     'DATABASE=mydb;'
  7.     'UID=root;'
  8.     'PWD=(whatever);'
  9.     'charset=utf8mb4;'
  10. )
  11. params = urllib.parse.quote_plus(connection_string)
  12. connection_uri = "mysql+pyodbc:///?odbc_connect=%s" % params