如果基于另一列中的值求和答案

【问题标题】：Sum if based on value in another column如果基于另一列中的值求和
【发布时间】：2013-01-31 17:28:04
【问题描述】：

在下面的代码中，我希望 AdminDuration 和 BreakDuration 根据 UserID 的值求和。目前我无法弄清楚，它将所有Durations 的值与ReasonCode 7 相加。结果每个UserId 都有相同的Duration（不是我想要的！）。

Select SkillTargetID AS UserID,
(SELECT sum(Duration) 
   from [t_Agent_Event_Detail] 
   where ReasonCode = 7
   and DateTime > convert(DATETIME, '2013-01-31 08:00', 21)) as AdminDuration,
(SELECT sum(Duration) 
   from [t_Agent_Event_Detail] 
   where ReasonCode = 6
   and DateTime > convert(DATETIME, '2013-01-31 08:00', 21) 
   and SkillTargetID = [t_Agent_Event_Detail].SkillTargetID) as BreakDuration 
from [t_Agent_Event_Detail]
GROUP BY SkillTargetID

【问题讨论】：

标签： sql sum

【解决方案1】：

如果我理解正确的话，应该是：

SELECT SkillTargetID AS UserID,
       sum(CASE WHEN ReasonCode = 7 THEN Duration ELSE 0 END) as AdminDuration,
       sum(CASE WHEN ReasonCode = 6 THEN Duration ELSE 0 END) as BreakDuration
FROM [t_Agent_Event_Detail]
WHERE DateTime > convert(DATETIME, '2013-01-31 08:00', 21)
GROUP BY SkillTargetID

【讨论】：