删除数据

使用 DELETE 语句删除数据。

示例如下：

假设有如下所示数据的表 t1 和 t2。其中，表 t2 为 KEY 分区表，且分区名由系统根据分区命令规则自动生成，即分区名为 p0、p1、p2、p3。

obclient> CREATE TABLE t1(c1 int primary key, c2 int);
Query OK, 0 rows affected (0.16 sec)
obclient> INSERT t1 VALUES(1,1),(2,2),(3,3),(4,4);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0
obclient> SELECT * FROM t1; 
+----+------+
| c1 | c2   |
+----+------+
|  1 |    1 |
|  2 |    2 |
|  3 |    3 |
|  4 |    4 |
+----+------+
4 rows in set (0.06 sec)

obclient> CREATE TABLE t2(c1 int primary key, c2 int) partition BY key(c1) partitions 4;
Query OK, 0 rows affected (0.19 sec)
obclient> INSERT INTO t2 VALUES(5,5),(1,1),(2,2),(3,3);
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0
obclient> SELECT * FROM t2;
+----+------+
| c1 | c2   |
+----+------+
|  5 |    5 |
|  1 |    1 |
|  2 |    2 |
|  3 |    3 |
+----+------+
4 rows in set (0.02 sec)

单表删除，删除 c1=2 的行，其中 c1 列为表 t1 中的 Primary Key。

obclient> DELETE FROM t1 WHERE c1 = 2;
Query OK, 1 row affected (0.02 sec)

obclient> SELECT * FROM t1;
+----+------+
| c1 | c2   |
+----+------+
|  1 |    1 |
|  3 |    3 |
|  4 |    4 |
+----+------+
3 rows in set (0.01 sec)

单表删除，删除表 t1 中按照 c2 列排序之后的第一行数据。

obclient> DELETE FROM t1 ORDER BY c2 LIMIT 1;
Query OK, 1 row affected (0.01 sec)

obclient> SELECT * FROM t1;
+----+------+
| c1 | c2   |
+----+------+
|  2 |    2 |
|  3 |    3 |
|  4 |    4 |
+----+------+
3 rows in set (0.00 sec)

单表删除，删除表 t2 的 p2 分区的数据。

obclient> SELECT * FROM t2 PARTITION(p2); 
+----+------+
| c1 | c2   |
+----+------+
|  1 |    1 |
|  2 |    2 |
|  3 |    3 |
+----+------+
3 rows in set (0.01 sec)

obclient> DELETE FROM t2  PARTITION(p2); 
Query OK, 3 rows affected (0.02 sec)

obclient> SELECT * FROM t2;
+----+------+
| c1 | c2   | 
+----+------+
|  5 |    5 |
+----+------+
1 row in set (0.02 sec)

多表删除，删除 t1、t2 表中 t1.c1 = t2.c1 的数据。

obclient> DELETE t1, t2 FROM t1, t2 WHERE t1.c1 = t2.c1;
Query OK, 3 rows affected (0.02 sec)

obclient> SELECT * FROM t1;
+----+------+
| c1 | c2   |
+----+------+
|  4 |    4 |
+----+------+
1 row in set (0.01 sec)

obclient> SELECT * FROM t2;
+----+------+
| c1 | c2   |
+----+------+ 
|  5 |    5 | 
+----+------+
1 row in set (0.01 sec)

多表删除，删除 t1、t2 表中 t1.c1 = t2.c1 的数据。

obclient> DELETE FROM t1, t2 USING t1, t2 WHERE t1.c1 = t2.c1;
Query OK, 4 rows affected (0.02 sec)

obclient> SELECT * FROM t1;
+----+------+
| c1 | c2   |
+----+------+
|  4 |    4 |
+----+------+
1 row in set (0.01 sec)

obclient> SELECT * FROM t2;
Empty set (0.01 sec)

更多 DELETE 语句相关的语法说明请参见《SQL 参考（MySQL 模式）》中 DELETE章节。

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