openGauss高级特性：附录：SQL语法（13）

DEALLOCATE

用于删除前面编写的预备语句。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。

DEALLOCATE [ PREPARE ] { name | ALL };

DECLARE

用于删除前面编写的预备语句。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。

1. declare a cursor:
DECLARE cursor_name [ BINARY ] [ NO SCROLL ]
    CURSOR [ { WITH | WITHOUT } HOLD ] FOR query ;

2. start an anonymous block:
[DECLARE [declare_statements]]
BEGIN
execution_statements
END;
/

DELETE

从指定的表里删除满足WHERE子句的行。如果WHERE子句不存在，将删除表中所有行，结果只保留表结构。

[ WITH [ RECURSIVE ] with_query [, ...] ]
DELETE [/*+ plan_hint */] FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ]
    [ USING using_list ]
    [ WHERE condition | WHERE CURRENT OF cursor_name ] [ LIMIT row_count ]
    [ RETURNING { * | { output_expr [ [ AS ] output_name ] } [, ...] } ];

DO

执行匿名代码块。

DO [ LANGUAGE lang_name ] code;

DROP AUDIT POLICY

删除一个审计策略。

DROP AUDIT POLICY [IF EXISTS] policy_name;

DROP CLIENT MASTER KEY

删除一个客户端加密主密钥(CMK)。

DROP CLIENT MASTER KEY [ IF EXISTS ] client_master_key_name [, ...];

DROP COLUMN ENCRYPTION KEY

删除一个列加密密钥(cek)。

DROP COLUMN ENCRYPTION KEY [ IF EXISTS ] client_column_key_name [, ...];

DROP DATA SOURCE

删除一个Data Source对象。

DROP DATA SOURCE [IF EXISTS] src_name [CASCADE | RESTRICT];

DROP DATABASE

删除一个数据库。

DROP DATABASE [ IF EXISTS ] database_name;

DROP DIRECTORY

删除指定的directory对象。

DROP DIRECTORY [ IF EXISTS ] directory_name;

DROP EVENT TRIGGER

删除一个事件触发器。

DROP EVENT TRIGGER [ IF EXISTS ] name [ CASCADE | RESTRICT ];

DROP EXTENSION

删除一个扩展。

DROP EXTENSION [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ];

DROP FOREIGN TABLE

删除指定的外表。

DROP FOREIGN TABLE [ IF EXISTS ]
table_name [, ...] [ CASCADE | RESTRICT ];

DROP FUNCTION

删除一个已存在的函数。

DROP FUNCTION [ IF EXISTS ] function_name [ ( [ {[ argmode ] [ argname ] argtype} [, ...] ] ) [ CASCADE | RESTRICT ] ];