DESCRIBE 语句 #
DESCRIBE 语句用于描述表或视图的 schema。
执行 DESCRIBE 语句 #
可以使用 TableEnvironment 的 executeSql() 方法执行 DESCRIBE 语句。如果 DESCRIBE 操作执行成功，executeSql() 方法会返回给定表的 schema，否则会抛出异常。
以下示例展示了如何在 TableEnvironment 中执行一条 DESCRIBE 语句。
可以使用 TableEnvironment 的 executeSql() 方法执行 DESCRIBE 语句。如果 DESCRIBE 操作执行成功，executeSql() 方法会返回给定表的 schema，否则会抛出异常。
以下示例展示了如何在 TableEnvironment 中执行一条 DESCRIBE 语句。
可以使用 TableEnvironment 的 execute_sql() 方法执行 DESCRIBE 语句。如果 DESCRIBE 操作执行成功，execute_sql() 方法会返回给定表的 schema，否则会抛出异常。
以下示例展示了如何在 TableEnvironment 中执行一条 DESCRIBE 语句。
DESCRIBE 语句可以在 SQL CLI 中执行。
以下示例展示了如何在 SQL CLI 中执行一条 DESCRIBE 语句。
TableEnvironment tableEnv = TableEnvironment.create(...);
// 注册名为 “Orders” 的表
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 (...)");
// 打印 schema
tableEnv.executeSql("DESCRIBE Orders").print();
// 打印 schema
tableEnv.executeSql("DESC Orders").print();
val tableEnv = TableEnvironment.create(...)
// 注册名为 “Orders” 的表
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 (...)")
// 打印 schema
tableEnv.executeSql("DESCRIBE Orders").print()
// 打印 schema
tableEnv.executeSql("DESC Orders").print()
table_env = TableEnvironment.create(...)
# 注册名为 “Orders” 的表
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 (...)");
# 打印 schema
table_env.execute_sql("DESCRIBE Orders").print()
# 打印 schema
table_env.execute_sql("DESC Orders").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;
上述示例的结果是：
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| 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
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| 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
+---------+-----------------------------+-------+-----------+---------------+----------------------------+---------------------------+
| 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
root
|-- user: BIGINT NOT NULL COMMENT 'this is primary key'
|-- product: VARCHAR(32)
|-- amount: INT
|-- ts: TIMESTAMP(3) *ROWTIME* COMMENT 'notice: watermark'
|-- ptime: TIMESTAMP(3) NOT NULL *PROCTIME* AS PROCTIME() COMMENT 'this is a computed column'
|-- WATERMARK FOR ts AS `ts` - INTERVAL '1' SECOND
|-- CONSTRAINT PK_3599338 PRIMARY KEY (user)
语法 #
{ DESCRIBE | DESC } [catalog_name.][db_name.]table_name