This documentation is for an unreleased version of Apache Flink. We recommend you use the latest stable version.
DESCRIBE Statements
DESCRIBE Statements #
DESCRIBE statements are used to describe the schema of a table or a view, or the metadata of a catalog.
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 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.
TableEnvironment tableEnv = TableEnvironment.create(...);
// register a table named "Orders"
tableEnv.executeSql(
"CREATE TABLE Orders (" +
" `user` BIGINT NOT NULl comment 'this is primary key'," +
" product VARCHAR(32)," +
" amount INT," +
" ts TIMESTAMP(3) comment 'notice: watermark'," +
" ptime AS PROCTIME() comment 'this is a computed column'," +
" PRIMARY KEY(`user`) NOT ENFORCED," +
" WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS" +
") with (...)");
// print the schema
tableEnv.executeSql("DESCRIBE Orders").print();
// print the schema
tableEnv.executeSql("DESC Orders").print();
// register a catalog named "cat2"
tableEnv.executeSql("CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db')");
// print the metadata
tableEnv.executeSql("DESCRIBE CATALOG cat2").print();
// print the complete metadata
tableEnv.executeSql("DESC CATALOG EXTENDED cat2").print();
val tableEnv = TableEnvironment.create(...)
// register a table named "Orders"
tableEnv.executeSql(
"CREATE TABLE Orders (" +
" `user` BIGINT NOT NULl comment 'this is primary key'," +
" product VARCHAR(32)," +
" amount INT," +
" ts TIMESTAMP(3) comment 'notice: watermark'," +
" ptime AS PROCTIME() comment 'this is a computed column'," +
" PRIMARY KEY(`user`) NOT ENFORCED," +
" WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS" +
") with (...)")
// print the schema
tableEnv.executeSql("DESCRIBE Orders").print()
// print the schema
tableEnv.executeSql("DESC Orders").print()
// register a catalog named "cat2"
tableEnv.executeSql("CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db')")
// print the metadata
tableEnv.executeSql("DESCRIBE CATALOG cat2").print()
// print the complete metadata
tableEnv.executeSql("DESC CATALOG EXTENDED cat2").print()
table_env = TableEnvironment.create(...)
# register a table named "Orders"
table_env.execute_sql( \
"CREATE TABLE Orders ("
" `user` BIGINT NOT NULl comment 'this is primary key',"
" product VARCHAR(32),"
" amount INT,"
" ts TIMESTAMP(3) comment 'notice: watermark',"
" ptime AS PROCTIME() comment 'this is a computed column',"
" PRIMARY KEY(`user`) NOT ENFORCED,"
" WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS"
") with (...)");
# print the schema
table_env.execute_sql("DESCRIBE Orders").print()
# print the schema
table_env.execute_sql("DESC Orders").print()
# register a catalog named "cat2"
table_env.execute_sql("CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db')")
# print the metadata
table_env.execute_sql("DESCRIBE CATALOG cat2").print()
# print the complete metadata
table_env.execute_sql("DESC CATALOG EXTENDED cat2").print()
Flink SQL> CREATE TABLE Orders (
> `user` BIGINT NOT NULl comment 'this is primary key',
> product VARCHAR(32),
> amount INT,
> ts TIMESTAMP(3) comment 'notice: watermark',
> ptime AS PROCTIME() comment 'this is a computed column',
> PRIMARY KEY(`user`) NOT ENFORCED,
> WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS
> ) with (
> ...
> );
[INFO] Table has been created.
Flink SQL> DESCRIBE Orders;
Flink SQL> DESC Orders;
Flink SQL> CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db');
[INFO] Execute statement succeeded.
Flink SQL> DESCRIBE CATALOG cat2;
Flink SQL> DESC CATALOG EXTENDED cat2;
The result of the above example is:
# DESCRIBE TABLE Orders
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| name | type | null | key | extras | watermark | comment |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| user | BIGINT | FALSE | PRI(user) | | | this is primary key |
| product | VARCHAR(32) | TRUE | | | | |
| amount | INT | TRUE | | | | |
| ts | TIMESTAMP(3) *ROWTIME* | TRUE | | | `ts` - INTERVAL '1' SECOND | notice: watermark |
| ptime | TIMESTAMP_LTZ(3) *PROCTIME* | FALSE | | AS PROCTIME() | | this is a computed column |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
5 rows in set
# DESCRIBE CATALOG cat2
+-----------+-------------------+
| info name | info value |
+-----------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
+-----------+-------------------+
3 rows in set
# DESCRIBE CATALOG EXTENDED cat2
+-------------------------+-------------------+
| info name | info value |
+-------------------------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
| option:default-database | db |
+-------------------------+-------------------+
4 rows in set
# DESCRIBE TABLE Orders
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| name | type | null | key | extras | watermark | comment |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| user | BIGINT | FALSE | PRI(user) | | | this is primary key |
| product | VARCHAR(32) | TRUE | | | | |
| amount | INT | TRUE | | | | |
| ts | TIMESTAMP(3) *ROWTIME* | TRUE | | | `ts` - INTERVAL '1' SECOND | notice: watermark |
| ptime | TIMESTAMP_LTZ(3) *PROCTIME* | FALSE | | AS PROCTIME() | | this is a computed column |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
5 rows in set
# DESCRIBE CATALOG cat2
+-----------+-------------------+
| info name | info value |
+-----------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
+-----------+-------------------+
3 rows in set
# DESCRIBE CATALOG EXTENDED cat2
+-------------------------+-------------------+
| info name | info value |
+-------------------------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
| option:default-database | db |
+-------------------------+-------------------+
4 rows in set
# DESCRIBE TABLE Orders
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| name | type | null | key | extras | watermark | comment |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| user | BIGINT | FALSE | PRI(user) | | | this is primary key |
| product | VARCHAR(32) | TRUE | | | | |
| amount | INT | TRUE | | | | |
| ts | TIMESTAMP(3) *ROWTIME* | TRUE | | | `ts` - INTERVAL '1' SECOND | notice: watermark |
| ptime | TIMESTAMP_LTZ(3) *PROCTIME* | FALSE | | AS PROCTIME() | | this is a computed column |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
5 rows in set
# DESCRIBE CATALOG cat2
+-----------+-------------------+
| info name | info value |
+-----------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
+-----------+-------------------+
3 rows in set
# DESCRIBE CATALOG EXTENDED cat2
+-------------------------+-------------------+
| info name | info value |
+-------------------------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
| option:default-database | db |
+-------------------------+-------------------+
4 rows in set
# DESCRIBE TABLE Orders
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| name | type | null | key | extras | watermark | comment |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| user | BIGINT | FALSE | PRI(user) | | | this is primary key |
| product | VARCHAR(32) | TRUE | | | | |
| amount | INT | TRUE | | | | |
| ts | TIMESTAMP(3) *ROWTIME* | TRUE | | | `ts` - INTERVAL '1' SECOND | notice: watermark |
| ptime | TIMESTAMP_LTZ(3) *PROCTIME* | FALSE | | AS PROCTIME() | | this is a computed column |
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
5 rows in set
# DESCRIBE CATALOG cat2
+-----------+-------------------+
| info name | info value |
+-----------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
+-----------+-------------------+
3 rows in set
# DESCRIBE CATALOG EXTENDED cat2
+-------------------------+-------------------+
| info name | info value |
+-------------------------+-------------------+
| name | cat2 |
| type | generic_in_memory |
| comment | |
| option:default-database | db |
+-------------------------+-------------------+
4 rows in set
Syntax #
- DESCRIBE TABLE
{ DESCRIBE | DESC } [catalog_name.][db_name.]table_name
- DESCRIBE CATALOG
{ DESCRIBE | DESC } CATALOG [EXTENDED] catalog_name