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更新时间：2024-11-12 GMT+08:00
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DEALLOCATE

功能描述

DEALLOCATE用于删除预备语句。

注意事项

  • 如果用户没有明确删除一个预备语句，那么它将在会话结束的时候被删除。
  • 语法中PREPARE关键字总被忽略。

语法格式

DEALLOCATE [ PREPARE ] { name | ALL };

参数说明

  • name

    将要删除的预备语句。

  • ALL

    删除所有预备语句。

示例

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--查看现有预备语句。
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name | statement | parameter_types 
------+-----------+-----------------
(0 rows)

--创建q1,q2,q3，q4四个预备语句。
gaussdb=# PREPARE q1 AS SELECT 1 AS a;
PREPARE
gaussdb=# PREPARE q2 AS SELECT 1 AS a;
PREPARE
gaussdb=# PREPARE q3 AS SELECT 1 AS a;
PREPARE
gaussdb=# PREPARE q4 AS SELECT 1 AS a;
PREPARE

--再次查看现有预备语句。
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name |          statement           | parameter_types 
------+------------------------------+-----------------
 q1   | PREPARE q1 AS SELECT 1 AS a; | {}
 q4   | PREPARE q4 AS SELECT 1 AS a; | {}
 q3   | PREPARE q3 AS SELECT 1 AS a; | {}
 q2   | PREPARE q2 AS SELECT 1 AS a; | {}
(4 rows)

--删除q4预备语句并查看剩余预备语句。
gaussdb=# DEALLOCATE q4;
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name |          statement           | parameter_types 
------+------------------------------+-----------------
 q1   | PREPARE q1 AS SELECT 1 AS a; | {}
 q3   | PREPARE q3 AS SELECT 1 AS a; | {}
 q2   | PREPARE q2 AS SELECT 1 AS a; | {}
(3 rows）

--删除所有预备语句并查看剩余预备语句。
gaussdb=# DEALLOCATE ALL;
DEALLOCATE ALL
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name | statement | parameter_types 
------+-----------+-----------------
(0 rows)
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