160 lines
3.3 KiB
Markdown
160 lines
3.3 KiB
Markdown
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`。
|
|
|
|
```sql
|
|
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。
|
|
|
|
```sql
|
|
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。
|
|
|
|
```sql
|
|
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。
|
|
|
|
```sql
|
|
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。
|
|
|
|
```sql
|
|
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。
|
|
|
|
```sql
|
|
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](../../10.sql-reference/5.sql-statement/23.DELETE.md)章节。
|