更新时间:2024-07-01 GMT+08:00
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关键字总会被忽略。
语法格式
1
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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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