DELETE

功能描述

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。

注意事项

• 本章节仅包含shark新增语法，原openGauss的DELETE语法未作删除和修改。原openGauss的DELETE语法请参考章节DELETE。
• 新增支持table_hint子句。

语法格式

单表删除：
[ WITH [ RECURSIVE ] with_query [, ...] ]
DELETE [/*+ plan_hint */] [FROM] [ ONLY ] table_name [ * ]
[ [ [partition_clause] [ [ AS ] alias ] [ table_hint_clause ] ] | [ [ [ AS ] alias ] [partitions_clause] ] ]
    [ USING using_list ]
    [ FROM from_list 
    [JOIN join_table ON join_condition]... ]
    [ WHERE condition | WHERE CURRENT OF cursor_name ]
    [ ORDER BY {expression [ [ ASC | DESC | USING operator ]
    [ LIMIT { count } ]
    [ RETURNING { * | { output_expr [ [ AS ] output_name ] } [, ...] } ];

多表删除：
[ WITH [ RECURSIVE ] with_query [, ...] ]
DELETE [/*+ plan_hint */] [FROM] 
    {[ ONLY ] table_name [ * ] [ [ [partition_clause] [ [ AS ] alias ] [ table_hint_clause ] ] | [ [ [ AS ] alias ] [partitions_clause] ] ]} [, ...]
    [ USING using_list ]
    [ FROM from_list 
    [JOIN join_table ON join_condition]... ]
    [ WHERE condition  ];
或
[ WITH [ RECURSIVE ] with_query [, ...] ]
DELETE [/*+ plan_hint */]
    {[ ONLY ] table_name [ * ] [ [ [partition_clause] [ [ AS ] alias ] [ table_hint_clause ] ] | [ [ [ AS ] alias ] [partitions_clause] ] ]} [, ...]
    [ FROM using_list ]
    [ WHERE condition ];

• 其中table_hint子句table_hint_clause为：

  WITH ( <table_hint> [, ...] ) 
  

参数说明

• JOIN

  JOIN包含 INNER JOIN，LEFT JOIN，RIGHT JOIN，FULL JOIN，CROSS JOIN。

• WITH ( <table_hint> [, …] )

  • 不同于SELECT子句，针对单个hint，WITH可选，针对DELETE子句，WITH必选，table_hint支持给出一个列表选项，列表通过逗号或者空格分隔，即WITH (hint1)、WITH (hint1, hint2, …)、WITH (hint1 hint2 …)均支持，(hint1)不支持。

  • 支持的hint包括NOLOCK、READUNCOMMITTED、UPDLOCK、REPEATABLEREAD、SERIALIZABLE、READCOMMITTED、TABLOCK、TABLOCKX、PAGLOCK、ROWLOCK、NOWAIT、READPAST、XLOCK、SNAPSHOT、NOEXPAND。

  • 当上述hint需要当做标识符，用于列名、变量名等，需要设置d_format_behavior_compat_options = 'enable_table_hint_identifier'，该变量默认值d_format_behavior_compat_options = ''。

  • 所有的hint仅语法支持，无实际含义。

  • 针对hint，会打印相关NOTICE信息。

table_hint子句示例

create table t1 (c1 int);

delete from t1 with (nolock) where c1 = 5;
NOTICE:  The nolock option is currently ignored

delete from t1 with (nolock, nowait) where c1 = 5;
NOTICE:  The nolock option is currently ignored
NOTICE:  The nowait option is currently ignored

delete from t1 with (nolock nowait) where c1 = 5;
NOTICE:  The nolock option is currently ignored
NOTICE:  The nowait option is currently ignored

相关链接

DELETE