using case statement in a where clause

Question

Hello I am missing something because my code errors.

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

I've attempted several combinations and each one errors at either the first equal sign or the second. What am I missing?

Answer 1

The branches of a case expression can only return values, not additional expressions to be evaluated in the where condition. You could, however, simulate this behavior with the and and or logical operators:

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

Note that you have makeup = 0 on both branches of the case expression in the question (or both sides of the or in the answer), so you could extract it out of it and simplify the condition a bit:

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