DESCRIBE Statements

DESCRIBE statements are used to describe the schema of a table or a view.

Run a DESCRIBE statement

DESCRIBE statements can be executed with the executeSql() method of the TableEnvironment, or executed in SQL CLI. The executeSql() method returns the schema of given table for a successful DESCRIBE operation, otherwise will throw an exception.

The following examples show how to run a DESCRIBE statement in TableEnvironment and in SQL CLI.

EnvironmentSettings settings = EnvironmentSettings.newInstance()...
TableEnvironment tableEnv = TableEnvironment.create(settings);
// register a table named "Orders"
tableEnv.executeSql(
        "CREATE TABLE Orders (" +
        " `user` BIGINT NOT NULl," +
        " product VARCHAR(32)," +
        " amount INT," +
        " ts TIMESTAMP(3)," +
        " ptime AS PROCTIME()," +
        " PRIMARY KEY(`user`) NOT ENFORCED," +
        " WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS" +
        ") with (...)");
// print the schema
tableEnv.executeSql("DESCRIBE Orders").print();

val settings = EnvironmentSettings.newInstance()...
val tableEnv = TableEnvironment.create(settings)
// register a table named "Orders"
 tableEnv.executeSql(
        "CREATE TABLE Orders (" +
        " `user` BIGINT NOT NULl," +
        " product VARCHAR(32)," +
        " amount INT," +
        " ts TIMESTAMP(3)," +
        " ptime AS PROCTIME()," +
        " PRIMARY KEY(`user`) NOT ENFORCED," +
        " WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS" +
        ") with (...)")
// print the schema
tableEnv.executeSql("DESCRIBE Orders").print()

settings = EnvironmentSettings.new_instance()...
table_env = StreamTableEnvironment.create(env, settings)
# register a table named "Orders"
table_env.execute_sql( \
        "CREATE TABLE Orders (" 
        " `user` BIGINT NOT NULl," 
        " product VARCHAR(32),"
        " amount INT,"
        " ts TIMESTAMP(3),"
        " ptime AS PROCTIME(),"
        " PRIMARY KEY(`user`) NOT ENFORCED,"
        " WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS"
        ") with (...)");
# print the schema
table_env.execute_sql("DESCRIBE Orders").print()

Flink SQL> CREATE TABLE Orders (
>  `user` BIGINT NOT NULl,
>  product VARCHAR(32),
>  amount INT,
>  ts TIMESTAMP(3),
>  ptime AS PROCTIME(),
>  PRIMARY KEY(`user`) NOT ENFORCED,
>  WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS
> ) with (
>  ...
> );
[INFO] Table has been created.
Flink SQL> DESCRIBE Orders;

The result of the above example is:

+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
|    name |                             type |  null |       key | computed column |                  watermark |
+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
|    user |                           BIGINT | false | PRI(user) |                 |                            |
| product |                      VARCHAR(32) |  true |           |                 |                            |
|  amount |                              INT |  true |           |                 |                            |
|      ts |           TIMESTAMP(3) *ROWTIME* |  true |           |                 | `ts` - INTERVAL '1' SECOND |
|   ptime | TIMESTAMP(3) NOT NULL *PROCTIME* | false |           |      PROCTIME() |                            |
+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
5 rows in set

+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
|    name |                             type |  null |       key | computed column |                  watermark |
+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
|    user |                           BIGINT | false | PRI(user) |                 |                            |
| product |                      VARCHAR(32) |  true |           |                 |                            |
|  amount |                              INT |  true |           |                 |                            |
|      ts |           TIMESTAMP(3) *ROWTIME* |  true |           |                 | `ts` - INTERVAL '1' SECOND |
|   ptime | TIMESTAMP(3) NOT NULL *PROCTIME* | false |           |      PROCTIME() |                            |
+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
5 rows in set

+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
|    name |                             type |  null |       key | computed column |                  watermark |
+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
|    user |                           BIGINT | false | PRI(user) |                 |                            |
| product |                      VARCHAR(32) |  true |           |                 |                            |
|  amount |                              INT |  true |           |                 |                            |
|      ts |           TIMESTAMP(3) *ROWTIME* |  true |           |                 | `ts` - INTERVAL '1' SECOND |
|   ptime | TIMESTAMP(3) NOT NULL *PROCTIME* | false |           |      PROCTIME() |                            |
+---------+----------------------------------+-------+-----------+-----------------+----------------------------+
5 rows in set

root
 |-- user: BIGINT NOT NULL
 |-- product: VARCHAR(32)
 |-- amount: INT
 |-- ts: TIMESTAMP(3) *ROWTIME*
 |-- ptime: TIMESTAMP(3) NOT NULL *PROCTIME* AS PROCTIME()
 |-- WATERMARK FOR ts AS `ts` - INTERVAL '1' SECOND
 |-- CONSTRAINT PK_3599338 PRIMARY KEY (user)

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Syntax

DESCRIBE [catalog_name.][db_name.]table_name