sql - 在 where 子句中使用 case 语句

Question

您好，我遗漏了一些东西，因为我的代码错误。

select * from ##ScheduleDetail SD
left join ##HolidayFilterTbl HF on SD.Scheduledate = HF.Testdate

where (ScheduleDate = testdate)
and
(Case 
 when HF.IsHoliday = 1 then (overtime = 1 and makeup = 0)
 else
(overtime = 0 and Makeup = 0)
end
)
and
DOW = 5 
order by ActivityStartTime

我尝试了几种组合，每个组合都在第一个等号或第二个等号处出错。我错过了什么？

Answer 1

case的分支表达式只能返回值，不能在 where 中计算额外的表达式健康)状况。但是，您可以使用 and 模拟这种行为。和 or逻辑运算符:

select    *
from      ##ScheduleDetail SD
left join ##HolidayFilterTbl HF on SD.Scheduledate = HF.Testdate
where     (ScheduleDate = testdate) and
          ((HF.IsHoliday = 1 and overtime = 1 and makeup = 0) or
           (overtime = 0 and Makeup = 0)) and
          DOW = 5 
order by  ActivityStartTime

请注意，您有 makeup = 0在 case 的两个分支上问题中的表达式(或答案中 or 的两侧)，因此您可以从中提取它并稍微简化条件:

select    *
from      ##ScheduleDetail SD
left join ##HolidayFilterTbl HF on SD.Scheduledate = HF.Testdate
where     ScheduleDate = testdate and
          makeup = 0 and
          ((HF.IsHoliday = 1 and overtime = 1) or
           overtime = 0) and
          DOW = 5 
order by  ActivityStartTime