MYSQL where 子句中的条件答案

【问题标题】：Conditional in MYSQL where clauseMYSQL where 子句中的条件
【发布时间】：2013-08-29 08:39:24
【问题描述】：

我有一个查询，如果名为 OrderBy 的标志为 1，那么它是一个日历事件，我需要检查两个日期时间字段之间的范围。而所有其他类型我们只检查您正在查看的日期。我研究了 if 语句，并看到许多建议使用案例的帖子，因此我尝试将其实现到我的查询中。我的查询需要 where 的条件。我知道我有语法问题，这就是为什么我在这里希望有人能指出正确的方法。

感谢您的宝贵时间

我的查询目前

SELECT          activities.*, 
                activitytypes.orderby 
FROM            activities 
LEFT OUTER JOIN activitytypes 
ON              activities.typeid = activitytypes.typeid 
WHERE           activities.userid = 86 
AND             activities.typeid NOT IN ( 5, 
                                          10, 
                                          11, 
                                          12, 
                                          19 ) 
AND 
                CASE 
                                WHEN activities.orderby = 1 THEN activities.starttime >= '2013-08-26 04:00:00' 
                                AND             activities.endtime <= '2013-08-27 04:00:00' 
                                ELSE activities.activitydate = '2013-08-26' 
                                order BY        activitytypes.orderby, 
                                                activities.starttime

【问题讨论】：

标签： mysql conditional case where

【解决方案1】：

只要使用足够的括号，您就可以使用 AND 和 OR 来做到这一点。

我还假设activities.OrderBy 可以为空。如果不是这种情况，您可以删除空检查：

SELECT activities.*, 
       activitytypes.orderby 
FROM   activities 
       LEFT OUTER JOIN activitytypes 
                    ON activities.typeid = activitytypes.typeid 
WHERE  activities.userid = 86 
       AND activities.typeid NOT IN ( 5, 10, 11, 12, 19 ) 
       AND ( ( activities.orderby = 1 
               AND activities.starttime >= '2013-08-26 04:00:00' 
               AND activities.endtime <= '2013-08-27 04:00:00' ) 
              OR ( ( activities.orderby IS NULL 
                      OR activities.orderby != 1 ) 
                   AND activities.activitydate = '2013-08-26' ) ) 
ORDER  BY activitytypes.orderby, 
          activities.starttime

或者，如果您仍想使用CASE，您只需使用END 关闭您的CASE 语句，如下所示：

SELECT          activities.*, 
                activitytypes.orderby 
FROM            activities 
LEFT OUTER JOIN activitytypes 
ON              activities.typeid = activitytypes.typeid 
WHERE           activities.userid = 86 
AND             activities.typeid NOT IN ( 5, 10, 11, 12, 19 ) 
AND             ( 
                  CASE 
                  WHEN activities.orderby = 1 THEN
                    activities.starttime >= '2013-08-26 04:00:00' AND activities.endtime <= '2013-08-27 04:00:00'
                  ELSE
                    activities.activitydate = '2013-08-26' 
                  END
                ) 
ORDER BY        activitytypes.orderby, 
                activities.starttime

【讨论】：