268 lines
5.0 KiB
Markdown
268 lines
5.0 KiB
Markdown
DELETE
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===========================
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描述
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-----------
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该语句用来删除表中符合条件的行，包括单表删除及多表删除两种方式。
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格式
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-----------
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```javascript
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Single-Table-Delete Syntax:
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DELETE [hint_options] FROM tbl_name
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[PARTITION (partition_name,...)]
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[WHERE where_condition]
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[ORDER BY order_expression_list]
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[LIMIT row_count]
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Multiple-Table-Delete Syntax:
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DELETE [hint_options] tbl_name[.*] [, tbl_name[.*]] ...
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FROM table_references
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[WHERE where_condition]
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Or:
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DELETE [hint_options] FROM tbl_name[.*] [, tbl_name[.*]] ...
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USING table_references
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[WHERE where_condition]
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where_condition:
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expression
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order_expression_list:
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order_expression [, order_expression ...]
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order_expression:
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expression [ASC | DESC]
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limit_row_count:
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INT_VALUE
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table_references:
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{tbl_name | joined_table | table_subquery | select_with_parens} [, ...]
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```
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参数解释
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-------------
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| **参数** | **描述** |
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|-----------------------|----------------------|
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| hint_options | 指定hint选项。 |
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| tbl_name | 指定需要删除的表名。 |
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| partition_name | 需要删除表的对应分区名。 |
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| where_condition | 删除的表需要满足的过滤条件。 |
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| order_expression_list | 删除的表的排序键列表。 |
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| row_count | 删除的表的行数指定，指定的值只能为整数。 |
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| table_references | 多表删除时指定的待选择的表序列。 |
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示例
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-----------
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示例表及数据基于以下定义：
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```javascript
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OceanBase(admin@test)>create table t1(c1 int primary key, c2 int);
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Query OK, 0 rows affected (0.16 sec)
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 1 |
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.06 sec)
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OceanBase(admin@test)>create table t2(c1 int primary key, c2 int) partition by key(c1) partitions 4;
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Query OK, 0 rows affected (0.19 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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| 1 | 1 |
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| 2 | 2 |
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| 3 | 3 |
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+----+------+
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4 rows in set (0.02 sec)
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```
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* 单表删除：删除 "c1=2" 的行，其中 c1 列为表 t1 中的 Primary Key。
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```javascript
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OceanBase(admin@test)>DELETE FROM t1 WHERE c1 = 2;
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Query OK, 1 row affected (0.02 sec)
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 1 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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3 rows in set (0.01 sec)
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```
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* 单表删除：删除表 t2 的按照 c2 列排序之后的第一行数据。
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```javascript
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OceanBase(admin@test)>DELETE FROM t1 ORDER BY c2 LIMIT 1;
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Query OK, 1 row affected (0.01 sec)
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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3 rows in set (0.00 sec)
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```
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* 单表删除：执行删除表 t2 的 p2 分区的数据。
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```javascript
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OceanBase(admin@test)>DELETE FROM t2 PARTITION(p2);
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Query OK, 3 rows affected (0.02 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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+----+------+
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1 row in set (0.02 sec)
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```
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* 多表删除：删除 t1，t2 表中 "t1.c1 = t2.c1" 的数据。
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```javascript
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OceanBase(admin@test)>DELETE t1, t2 FROM t1, t2 WHERE t1.c1 = t2.c1;
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Query OK, 3 rows affected (0.02 sec)
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 4 | 4 |
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+----+------+
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1 row in set (0.01 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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+----+------+
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1 row in set (0.01 sec)
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```
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* 多表删除：删除 t1，t2 表中 "t1.c1 = t2.c1" 的数据。
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```javascript
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OceanBase(admin@test)>DELETE FROM t1, t2 USING t1, t2 WHERE t1.c1 = t2.c1;
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Query OK, 4 rows affected (0.02 sec)
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OceanBase(admin@test)>select * from t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 4 | 4 |
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+----+------+
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1 row in set (0.01 sec)
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OceanBase(admin@test)>select * from t2;
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Empty set (0.01 sec)
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```
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* 多表删除：删除 t2 表中的 p2 分区中和 t1 表中 "t1.c1 = t2.c1" 的数据。
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```javascript
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OceanBase(admin@test)>DELETE t2 FROM t1,t2 PARTITION(p2) WHERE t1.c1 = t2.c1;
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Query OK, 3 rows affected (0.02 sec)
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OceanBase(admin@test)>select * from t2;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 5 | 5 |
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+----+------+
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1 row in set (0.01 sec)
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```
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* 对可更新视图v进行删除操作
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```javascript
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OceanBase(admin@test)>create view v as select * from t1;
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Query OK, 0 rows affected (0.07 sec)
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OceanBase(admin@test)>delete from v where v.c1 = 1;
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Query OK, 1 row affected (0.02 sec)
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OceanBase(admin@test)>select * from v;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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3 rows in set (0.01 sec)
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```
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注意事项
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-------------
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不管是多表删除还是单表删除都不支持直接对子查询进行删除操作，比如：
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`delete from (select * from t1);`
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