【MySQL】基本查询(下)-海口c网

【MySQL】基本查询(下)

article/2025/7/12 19:50:41

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本篇主题：【MySQL】基本查询(下)
发布时间：2025.2.18
隶属专栏：MySQL

在这里插入图片描述

Update

语法

UPDATE table_name SET column = expr [, column = expr ...][WHERE ...] [ORDER BY ...] [LIMIT ...]

对查询到的结果进行列值更新

案例

将孙悟空同学的数学成绩变更为 80 分

mysql> select name, math from exam_result;
+-----------+------+
| name      | math |
+-----------+------+
| 唐三藏    |   98 |
| 孙悟空    |   78 |
| 猪悟能    |   98 |
| 曹孟德    |   84 |
| 刘玄德    |   85 |
| 孙权      |   73 |
| 宋公明    |   65 |
+-----------+------+
7 rows in set (0.00 sec)mysql> update exam_result set math=80 where name='孙悟空';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0mysql> select name, math from exam_result;
+-----------+------+
| name      | math |
+-----------+------+
| 唐三藏    |   98 |
| 孙悟空    |   80 |
| 猪悟能    |   98 |
| 曹孟德    |   84 |
| 刘玄德    |   85 |
| 孙权      |   73 |
| 宋公明    |   65 |
+-----------+------+
7 rows in set (0.00 sec)

将曹孟德同学的数学成绩变更为 60 分，语文成绩变更为 70 分

mysql> select * from exam_result;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  1 | 唐三藏    |      67 |   98 |      56 |
|  2 | 孙悟空    |      87 |   80 |      77 |
|  3 | 猪悟能    |      88 |   98 |      90 |
|  4 | 曹孟德    |      82 |   84 |      67 |
|  5 | 刘玄德    |      55 |   85 |      45 |
|  6 | 孙权      |      70 |   73 |      78 |
|  7 | 宋公明    |      75 |   65 |      30 |
+----+-----------+---------+------+---------+
7 rows in set (0.00 sec)mysql> update exam_result set math=60, chinese=70  where name='曹孟德';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0mysql> select * from exam_result;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  1 | 唐三藏    |      67 |   98 |      56 |
|  2 | 孙悟空    |      87 |   80 |      77 |
|  3 | 猪悟能    |      88 |   98 |      90 |
|  4 | 曹孟德    |      70 |   60 |      67 |
|  5 | 刘玄德    |      55 |   85 |      45 |
|  6 | 孙权      |      70 |   73 |      78 |
|  7 | 宋公明    |      75 |   65 |      30 |
+----+-----------+---------+------+---------+
7 rows in set (0.00 sec)

将总成绩倒数前三的 3 位同学的数学成绩加上 30 分

mysql> select name, math+chinese+english total from exam_result order by total asc limit 3;
+-----------+-------+
| name      | total |
+-----------+-------+
| 宋公明    |   170 |
| 刘玄德    |   185 |
| 曹孟德    |   197 |
+-----------+-------+
3 rows in set (0.00 sec)mysql> update exam_result set math=math+30 order by chinese+math+english limit 3;
Query OK, 3 rows affected (0.02 sec)
Rows matched: 3  Changed: 3  Warnings: 0mysql> select name, math+chinese+english total from exam_result;
+-----------+-------+
| name      | total |
+-----------+-------+
| 唐三藏    |   221 |
| 孙悟空    |   244 |
| 猪悟能    |   276 |
| 曹孟德    |   227 |
| 刘玄德    |   215 |
| 孙权      |   221 |
| 宋公明    |   200 |
+-----------+-------+
7 rows in set (0.00 sec)

将所有同学的语文成绩更新为原来的 2 倍

注意：更新全表的语句慎用！

mysql> select * from exam_result;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  1 | 唐三藏