154 lines
3.3 KiB
Markdown
154 lines
3.3 KiB
Markdown
更新数据
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=========================
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使用 `UPDATE` 语句修改表中的字段值。
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示例如下：
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创建示例表 `t1` 和 `t2`。
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```sql
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obclient> 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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obclient> INSERT t1 VALUES(1,1),(2,2),(3,3),(4,4);
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Query OK, 4 rows affected (0.02 sec)
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Records: 4 Duplicates: 0 Warnings: 0
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obclient> 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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obclient> 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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obclient> INSERT t2 VALUES(5,5),(1,1),(2,2),(3,3);
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Query OK, 4 rows affected (0.01 sec)
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Records: 4 Duplicates: 0 Warnings: 0
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obclient> 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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* 将表 `t1` 中 `t1.c1=1` 对应的那一行数据的 `c2` 列值修改为 `100`。
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```sql
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obclient> UPDATE t1 SET t1.c2 = 100 WHERE t1.c1 = 1;
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Query OK, 1 row affected (0.02 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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obclient> SELECT * FROM t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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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 (0.01 sec)
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```
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* 将表 `t1` 中按照 `c2` 列排序的前两行数据的 `c2` 列值修改为 `100`。
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```sql
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obclient> UPDATE t1 set t1.c2 = 100 ORDER BY c2 LIMIT 2;
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Query OK, 2 rows affected (0.02 sec)
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Rows matched: 2 Changed: 2 Warnings: 0
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obclient> SELECT * FROM t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 100 |
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| 3 | 3 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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* 将表 `t2` 中 `p2` 分区的数据中 `t2.c1 > 2` 的对应行数据的 `c2` 列值修改为 `100`。
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```sql
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obclient> SELECT * FROM t2 partition (p2);
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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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+----+------+
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3 rows in set (0.01 sec)
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obclient> UPDATE t2 partition(p2) SET t2.c2 = 100 WHERE t2.c1 > 2;
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Query OK, 1 row affected (0.02 sec)
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Rows matched: 1 Changed: 1 Warnings: 0
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obclient> SELECT * FROM t2 partition (p2);
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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 | 100 |
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+----+------+
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3 rows in set (0.00 sec)
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```
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* 修改多个表。对于表 `t1` 和表 `t2` 中满足 `t1.c2 = t2.c2` 对应行的数据，将表 `t1` 中的 `c2` 列值修改为 `100`，表 `t2` 中的 `c2` 列值修改为 `200`。
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```sql
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obclient> UPDATE t1,t2 SET t1.c2 = 100, t2.c2 = 200 WHERE t1.c2 = t2.c2;
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Query OK, 6 rows affected (0.03 sec)
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Rows matched: 6 Changed: 6 Warnings: 0
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obclient> SELECT * FROM t1;
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+----+------+
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| c1 | c2 |
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+----+------+
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| 1 | 100 |
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| 2 | 100 |
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| 3 | 100 |
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| 4 | 4 |
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+----+------+
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4 rows in set (0.00 sec)
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obclient> 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 | 200 |
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| 2 | 200 |
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| 3 | 200 |
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+----+------+
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4 rows in set (0.01 sec)
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```
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更多 `UPDATE` 语句相关的语法请参见《SQL 参考（MySQL 模式）》中 [UPDATE](../../10.sql-reference/5.sql-statement/61.UPDATE.md)章节。
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