case 语句匹配顺序

<pre name="code" class="sql">mysql> select * from ClientLoginDevice;
+--------------+
| machineModel |
+--------------+
| Android01    |
| Android02    |
| Android03    |
| Androidpc    |
| ios01        |
| ios02        |
| ios03        |
| ios04        |
| iospc        |
| pc01         |
| pc02         |
+--------------+
11 rows in set (0.00 sec)

mysql> SELECT machineModel,
    ->             CASE
    ->                 WHEN machineModel LIKE '%Android%' THEN 'Android'
    ->                 WHEN machineModel LIKE '%ios%' THEN 'ios'
    ->                 WHEN machineModel LIKE '%wechat%' THEN 'wechat'
    ->                 ELSE 'pc'
    ->             END AS machineModel
    ->     FROM ClientLoginDevice
    -> GROUP BY machineModel;
+--------------+--------------+
| machineModel | machineModel |
+--------------+--------------+
| Android01    | Android      |
| Android02    | Android      |
| Android03    | Android      |
| Androidpc    | Android      |
| ios01        | ios          |
| ios02        | ios          |
| ios03        | ios          |
| ios04        | ios          |
| iospc        | ios          |
| pc01         | pc           |
| pc02         | pc           |
+--------------+--------------+
11 rows in set, 1 warning (0.00 sec)

可以看到Androidpc 同时匹配Android和pc,但是统计时都算入到Android 类型

iospc 也是同样的道理