MySQL 如何在使用UPDATE查询时使用MySQL CASE语句

要在使用UPDATE查询时使用MySQL CASE语句，可以使用CASE语句。让我们首先创建一个表 –

mysql> create table DemoTable
  (
  UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserScore int
  );
Query OK, 0 rows affected (0.29 sec)

使用插入命令将一些记录插入该表 –

mysql> insert into DemoTable(UserScore) values(100);
Query OK, 1 row affected (0.22 sec)

mysql> insert into DemoTable(UserScore) values(110);
Query OK, 1 row affected (0.07 sec)

mysql> insert into DemoTable(UserScore) values(120);
Query OK, 1 row affected (0.08 sec)

mysql> insert into DemoTable(UserScore) values(200);
Query OK, 1 row affected (0.05 sec)

mysql> insert into DemoTable(UserScore) values(230);
Query OK, 1 row affected (0.12 sec)

mysql> insert into DemoTable(UserScore) values(250);
Query OK, 1 row affected (0.03 sec)

mysql> insert into DemoTable(UserScore) values(270);
Query OK, 1 row affected (0.06 sec)

使用select语句显示表中的所有记录 –

mysql> select *from DemoTable;

这将产生以下输出 –

+--------+-----------+
| UserId | UserScore |
+--------+-----------+
|      1 |       100 |
|      2 |       110 |
|      3 |       120 |
|      4 |       200 |
|      5 |       230 |
|      6 |       250 |
|      7 |       270 |
+--------+-----------+
7 rows in set (0.00 sec)

以下是在使用UPDATE查询时使用CASE语句的查询 –

mysql> update DemoTable
   set UserScore =
   CASE
      WHEN UserScore BETWEEN 100 AND 120
         THEN UserScore + 5
      WHEN UserScore BETWEEN 130 AND 230
         THEN UserScore +10
      WHEN UserScore >=250
         THEN UserScore * 5
      ELSE UserScore
   END;
Query OK, 7 rows affected (0.06 sec)
Rows matched: 7 Changed: 7 Warnings: 0

现在，您可以再次从表中显示所有记录 –

mysql> select *from DemoTable;

这将产生以下输出 –

+--------+-----------+
| UserId | UserScore |
+--------+-----------+
|      1 |       105 |
|      2 |       115 |
|      3 |       125 |
|      4 |       210 |
|      5 |       240 |
|      6 |      1250 |
|      7 |      1350 |
+--------+-----------+
7 rows in set (0.00 sec)