GitBook: [master] one page modified

05-ying-yong-kai-fa/04-table-api-and-sql/sql/show-yu-ju.md

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 # SHOW语句
 
+SHOW语句用于列出所有catalog、或当前catalog中的所有数据库，或当前catalog和当前数据库的所有表/视图，或显示当前目录和数据库，或列出所有函数，包括临时系统函数，系统当前catalog和当前数据库中的函数，临时catalog函数以及catalog函数。
+
+Flink SQL现在支持以下SHOW语句：
+
+* SHOW CATALOGS
+* SHOW CURRENT CATALOG
+* SHOW DATABASES
+* SHOW CURRENT DATABASE
+* SHOW TABLES
+* SHOW VIEWS
+* SHOW FUNCTIONS
+
+## 运行一个SHOW语句
+
+可以使用`TableEnvironment`的`executeSql()`方法执行`SHOW`语句。`executeSql()`方法为成功的SHOW操作返回对象，否则将抛出异常。
+
+以下示例演示如何在`TableEnvironment`中运行`show`语句。
+
+{% tabs %}
+{% tab title="Java" %}
+```java
+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 |
+// +------------+
+
+// create a view
+tEnv.executeSql("CREATE VIEW my_view AS ...");
+// show views
+tEnv.executeSql("SHOW VIEWS").print();
+// +-----------+
+// | view name |
+// +-----------+
+// |   my_view |
+// +-----------+
+
+// show functions
+tEnv.executeSql("SHOW FUNCTIONS").print();
+// +---------------+
+// | function name |
+// +---------------+
+// |           mod |
+// |        sha256 |
+// |           ... |
+// +---------------+
+```
+{% endtab %}
+
+{% tab title="Scala" %}
+```scala
+val env = StreamExecutionEnvironment.getExecutionEnvironment()
+val tEnv = StreamTableEnvironment.create(env)
+
+// show catalogs
+tEnv.executeSql("SHOW CATALOGS").print()
+// +-----------------+
+// |    catalog name |
+// +-----------------+
+// | default_catalog |
+// +-----------------+
+
+// show databases
+tEnv.executeSql("SHOW DATABASES").print()
+// +------------------+
+// |    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 |
+// +------------+
+
+// create a view
+tEnv.executeSql("CREATE VIEW my_view AS ...")
+// show views
+tEnv.executeSql("SHOW VIEWS").print()
+// +-----------+
+// | view name |
+// +-----------+
+// |   my_view |
+// +-----------+
+
+// show functions
+tEnv.executeSql("SHOW FUNCTIONS").print()
+// +---------------+
+// | function name |
+// +---------------+
+// |           mod |
+// |        sha256 |
+// |           ... |
+// +---------------+
+```
+{% endtab %}
+
+{% tab title="Python" %}
+```python
+settings = EnvironmentSettings.new_instance()...
+table_env = StreamTableEnvironment.create(env, settings)
+
+# show catalogs
+table_env.execute_sql("SHOW CATALOGS").print()
+# +-----------------+
+# |    catalog name |
+# +-----------------+
+# | default_catalog |
+# +-----------------+
+
+# show databases
+table_env.execute_sql("SHOW DATABASES").print()
+# +------------------+
+# |    database name |
+# +------------------+
+# | default_database |
+# +------------------+
+
+# create a table
+table_env.execute_sql("CREATE TABLE my_table (...) WITH (...)")
+# show tables
+table_env.execute_sql("SHOW TABLES").print()
+# +------------+
+# | table name |
+# +------------+
+# |   my_table |
+# +------------+
+
+# create a view
+table_env.execute_sql("CREATE VIEW my_view AS ...")
+# show views
+table_env.execute_sql("SHOW VIEWS").print()
+# +-----------+
+# | view name |
+# +-----------+
+# |   my_view |
+# +-----------+
+
+# show functions
+table_env.execute_sql("SHOW FUNCTIONS").print()
+# +---------------+
+# | function name |
+# +---------------+
+# |           mod |
+# |        sha256 |
+# |           ... |
+# +---------------+
+```
+{% endtab %}
+
+{% tab title="SQL CLI" %}
+```sql
+Flink SQL> SHOW CATALOGS;
+default_catalog
+
+Flink SQL> SHOW DATABASES;
+default_database
+
+Flink SQL> CREATE TABLE my_table (...) WITH (...);
+[INFO] Table has been created.
+
+Flink SQL> SHOW TABLES;
+my_table
+
+Flink SQL> CREATE VIEW my_view AS ...;
+[INFO] View has been created.
+
+Flink SQL> SHOW VIEWS;
+my_view
+
+Flink SQL> SHOW FUNCTIONS;
+mod
+sha256
+...
+```
+{% endtab %}
+{% endtabs %}
+
+## 显示Catalog
+
+```text
+SHOW CATALOGS
+```
+
+显示所有Catalog。
+
+## 显示当前Catalog
+
+```text
+SHOW CURRENT CATALOG
+```
+
+显示当前Catalog。
+
+### 显示数据库 <a id="show-databases"></a>
+
+```text
+SHOW DATABASES
+```
+
+显示当前Catalog中的所有数据库。
+
+### 显示当前数据库 <a id="show-current-database"></a>
+
+```text
+SHOW CURRENT DATABASE
+```
+
+显示当前数据库。
+
+### 显示表 <a id="show-tables"></a>
+
+```text
+SHOW TABLES
+```
+
+显示当前Catalog和当前数据库中的所有表。
+
+### 显示视图 <a id="show-views"></a>
+
+```text
+SHOW VIEWS
+```
+
+显示当前Catalog和当前数据库中的所有视图。
+
+### 显示函数 <a id="show-functions"></a>
+
+```text
+SHOW FUNCTIONS
+```
+
+在当前Catalog和当前数据库中显示所有函数，包括临时系统函数，系统函数，临时Catalog函数和Catalog函数。  
+
+