Flink SQL: SHOW Statements

SHOW Statements

SHOW statements are used to list objects within their corresponding parent, such as catalogs, databases, tables and views, columns, functions, and modules. See the individual commands for more details and additional options.
SHOW语句用于列出相应父级中的对象，如目录、数据库、表和视图、列、函数和模块。有关详细信息和其他选项，请参见各个命令。

SHOW CREATE statements are used to print a DDL statement with which a given object can be created. The currently ‘SHOW CREATE’ statement is only available in printing DDL statement of the given table and view.
SHOW CREATE语句用于显示可以创建给定对象的DDL语句。当前的“SHOW CREATE”语句仅在显示给定表和视图的DDL语句时可用。

Flink SQL supports the following SHOW statements for now:
Flink SQL目前支持以下SHOW语句：

• SHOW CATALOGS
• SHOW CURRENT CATALOG
• SHOW DATABASES
• SHOW CURRENT DATABASE
• SHOW TABLES
• SHOW CREATE TABLE
• SHOW COLUMNS
• SHOW VIEWS
• SHOW CREATE VIEW
• SHOW FUNCTIONS
• SHOW MODULES
• SHOW JARS

Run a SHOW statement

Java
SHOW statements can be executed with the executeSql() method of the TableEnvironment. The executeSql() method returns objects for a successful SHOW operation, otherwise will throw an exception.
SHOW语句可以使用TableEnvironment的executeSql()方法执行。executeSql()方法为成功的SHOW操作返回对象，否则将引发异常。

The following examples show how to run a SHOW statement in TableEnvironment.
以下示例演示如何在TableEnvironment中运行show语句。

StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tEnv = StreamTableEnvironment.create(env);

// show catalogs
tEnv.executeSql("SHOW CATALOGS").print();
// +-----------------+
// |    catalog name |
// +-----------------+
// | default_catalog |
// +-----------------+

// show current catalog
tEnv.executeSql("SHOW CURRENT CATALOG").print();
// +----------------------+
// | current catalog name |
// +----------------------+
// |      default_catalog |
// +----------------------+

// show databases
tEnv.executeSql("SHOW DATABASES").print();
// +------------------+
// |    database name |
// +------------------+
// | default_database |
// +------------------+

// show current database
tEnv.executeSql("SHOW CURRENT DATABASE").print();
// +-----------------------+
// | current database name |
// +-----------------------+
// |      default_database |
// +-----------------------+

// create a table
tEnv.executeSql("CREATE TABLE my_table (...) WITH (...)");
// show tables
tEnv.executeSql("SHOW TABLES").print();
// +------------+
// | table name |
// +------------+
// |   my_table |
// +------------+

// show create table
tEnv.executeSql("SHOW CREATE TABLE my_table").print();
// CREATE TABLE `default_catalog`.`default_db`.`my_table` (
//   ...
// ) WITH (
//   ...
// )

// show columns
tEnv.executeSql("SHOW COLUMNS FROM my_table LIKE '%f%'").print();
// +--------+-------+------+-----+--------+-----------+
// |   name |  type | null | key | extras | watermark |
// +--------+-------+------+-----+--------+-----------+
// | field2 | BYTES | true |     |        |           |
// +--------+-------+------+-----+--------+-----------+


// create a view
tEnv.executeSql("CREATE VIEW my_view AS SELECT * FROM my_table");
// show views
tEnv.executeSql("SHOW VIEWS").print();
// +-----------+
// | view name |
// +-----------+
// |   my_view |
// +-----------+

// show create view
tEnv.executeSql("SHOW CREATE VIEW my_view").print();
// CREATE VIEW `default_catalog`.`default_db`.`my_view`(`field1`, `field2`, ...) as
// SELECT *
// FROM `default_catalog`.`default_database`.`my_table`

// show functions
tEnv.executeSql("SHOW FUNCTIONS").
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