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  • 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


    
                                        
    
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  • 原文地址:https://www.cnblogs.com/hzcya1995/p/13351156.html
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