mysql

Allows SELECT queries to be performed on data that is stored on a remote MySQL server.

  1. mysql('host:port', 'database', 'table', 'user', 'password'[, replace_query, 'on_duplicate_clause']);

Parameters

  • host:port — MySQL server address.
  • database — Remote database name.
  • table — Remote table name.
  • user — MySQL user.
  • password — User password.
  • replace_query — Flag that converts INSERT INTO queries to REPLACE INTO. If replace_query=1, the query is replaced.

  • on_duplicate_clause — The ON DUPLICATE KEY on_duplicate_clause expression that is added to the INSERT query.

    Example: INSERT INTO t (c1,c2) VALUES ('a', 2) ON DUPLICATE KEY UPDATE c2 = c2 + 1, where on_duplicate_clause is UPDATE c2 = c2 + 1. See the MySQL documentation to find which on_duplicate_clause you can use with the ON DUPLICATE KEY clause.

    To specify on_duplicate_clause you need to pass 0 to the replace_query parameter. If you simultaneously pass replace_query = 1 and on_duplicate_clause, ClickHouse generates an exception.

Simple WHERE clauses such as =, !=, >, >=, <, <= are currently executed on the MySQL server.

The rest of the conditions and the LIMIT sampling constraint are executed in ClickHouse only after the query to MySQL finishes.

Returned Value

A table object with the same columns as the original MySQL table.

Usage Example

Table in MySQL:

  1. mysql> CREATE TABLE `test`.`test` (
  2.     ->   `int_id` INT NOT NULL AUTO_INCREMENT,
  3.     ->   `int_nullable` INT NULL DEFAULT NULL,
  4.     ->   `float` FLOAT NOT NULL,
  5.     ->   `float_nullable` FLOAT NULL DEFAULT NULL,
  6.     ->   PRIMARY KEY (`int_id`));
  7. Query OK, 0 rows affected (0,09 sec)
  9. mysql> insert into test (`int_id`, `float`) VALUES (1,2);
  10. Query OK, 1 row affected (0,00 sec)
  12. mysql> select * from test;
  13. +--------+--------------+-------+----------------+
  14. | int_id | int_nullable | float | float_nullable |
  15. +--------+--------------+-------+----------------+
  16. |      1 |         NULL |     2 |           NULL |
  17. +--------+--------------+-------+----------------+
  18. 1 row in set (0,00 sec)

Selecting data from ClickHouse:

  1. SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123')
  1. ┌─int_id─┬─int_nullable─┬─float─┬─float_nullable─┐
  2. │      1 │         ᴺᵁᴸᴸ │     2 │           ᴺᵁᴸᴸ │
  3. └────────┴──────────────┴───────┴────────────────┘

See Also