DESCRIBE Statements
This documentation is for an out-of-date version of Apache Flink. We recommend you use the latest stable version.
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. 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.
DESCRIBE statements can be executed with the execute_sql() method of the TableEnvironment. The execute_sql() 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.
DESCRIBE statements can be executed in SQL CLI.
The following examples show how to run a DESCRIBE statement 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 setroot
|-- 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)Syntax
DESCRIBE [catalog_name.][db_name.]table_name