使用 UPDATE 语句修改表中的字段值。

    示例如下：

    创建示例表 t1 和 t2。

    1. obclient> CREATE TABLE t1(c1 int primary key, c2 int);
    2. Query OK, 0 rows affected (0.16 sec)
    3. obclient> INSERT t1 VALUES(1,1),(2,2),(3,3),(4,4);
    4. Query OK, 4 rows affected (0.02 sec)
    5. Records: 4  Duplicates: 0  Warnings: 0
    6. obclient> SELECT * FROM t1;
    7. +----+------+
    8. | c1 | c2   |
    9. +----+------+
    10. |  1 |    1 |
    11. |  2 |    2 |
    12. |  3 |    3 |
    13. |  4 |    4 |
    14. +----+------+
    15. 4 rows in set (0.06 sec)
    17. obclient> CREATE TABLE t2(c1 int primary key, c2 int) partition by key(c1) partitions 4;
    18. Query OK, 0 rows affected(0.19 sec)
    19. obclient> INSERT t2 VALUES(5,5),(1,1),(2,2),(3,3);
    20. Query OK, 4 rows affected (0.01 sec)
    21. Records: 4  Duplicates: 0  Warnings: 0
    22. obclient> SELECT * FROM t2;
    23. +----+------+
    24. | c1 | c2   |
    25. +----+------+
    26. |  5 |    5 |
    27. |  1 |    1 |
    28. |  2 |    2 |
    29. |  3 |    3 |
    30. +----+------+
    31. 4 rows in set (0.02 sec)

    • 将表 t1 中 t1.c1=1 对应的那一行数据的 c2 列值修改为 100。

      1. obclient> UPDATE t1 SET t1.c2 = 100 WHERE t1.c1 = 1;
      2. Query OK, 1 row affected (0.02 sec)
      3. Rows matched: 1  Changed: 1  Warnings: 0
      5. obclient> SELECT * FROM t1;
      6. +----+------+
      7. | c1 | c2   |
      8. +----+------+
      9. |  1 |  100 |
      10. |  2 |    2 |
      11. |  3 |    3 |
      12. |  4 |    4 |
      13. +----+------+
      14. 4 rows in set (0.01 sec)

    • 将表 t1 中按照 c2 列排序的前两行数据的 c2 列值修改为 100。

      1. obclient> UPDATE t1 set t1.c2 = 100 ORDER BY c2 LIMIT 2;
      2. Query OK, 2 rows affected (0.02 sec)
      3. Rows matched: 2  Changed: 2  Warnings: 0
      5. obclient> SELECT * FROM t1;
      6. +----+------+
      7. | c1 | c2   |
      8. +----+------+
      9. |  1 |  100 |
      10. |  2 |  100 |
      11. |  3 |    3 |
      12. |  4 |    4 |
      13. +----+------+
      14. 4 rows in set (0.01 sec)

    • 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。

      1. obclient> SELECT * FROM t2 partition (p2);
      2. +----+------+
      3. | c1 | c2   |
      4. +----+------+
      5. |  1 |    1 |
      6. |  2 |    2 |
      7. |  3 |    3 |
      8. +----+------+
      9. 3 rows in set (0.01 sec)
      11. obclient> UPDATE t2 partition(p2) SET t2.c2 = 100 WHERE t2.c1 > 2;
      12. Query OK, 1 row affected (0.02 sec)
      13. Rows matched: 1  Changed: 1  Warnings: 0
      15. obclient> SELECT * FROM t2 partition (p2);
      16. +----+------+
      17. | c1 | c2   |
      18. +----+------+
      19. |  1 |    1 |
      20. |  2 |    2 |
      21. |  3 |  100 |
      22. +----+------+
      23. 3 rows in set (0.00 sec)

    • 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。

      1. obclient> UPDATE t1,t2 SET t1.c2 = 100, t2.c2 = 200 WHERE t1.c2 = t2.c2;
      2. Query OK, 6 rows affected (0.03 sec)
      3. Rows matched: 6  Changed: 6  Warnings: 0
      5. obclient> SELECT * FROM t1;
      6. +----+------+
      7. | c1 | c2   |
      8. +----+------+
      9. |  1 |  100 |
      10. |  2 |  100 |
      11. |  3 |  100 |
      12. |  4 |    4 |
      13. +----+------+
      14. 4 rows in set (0.00 sec)
      16. obclient> SELECT * FROM t2;
      17. +----+------+
      18. | c1 | c2   |
      19. +----+------+
      20. |  5 |    5 |
      21. |  1 |  200 |
      22. |  2 |  200 |
      23. |  3 |  200 |
      24. +----+------+
      25. 4 rows in set (0.01 sec)

    更多 UPDATE 语句相关的语法请参见《SQL 参考（MySQL 模式）》中 UPDATE 章节。