Using an 'IN' predicate with CASE statements in the WHERE clause for SQL Server

Question

Here's a SQL query that works absolutely fine:

DECLARE @IncludePTO AS CHAR
SET @IncludePTO = 'Y'

SELECT     
   HQCO.HQCo, HQCO.Name, PREH.PRDept, PREH.Craft, HRRM.PositionCode, PRTH.Employee, 
   PREH.LastName, PREH.FirstName, SUM(PRTH.Hours) AS Hrs
FROM PREH 
INNER JOIN HRRM ON PREH.PRCo = HRRM.HRCo AND PREH.Employee = HRRM.HRRef 
INNER JOIN PRTH ON PREH.PRCo = PRTH.PRCo AND PREH.Employee = PRTH.Employee 
INNER JOIN HQCO ON PRTH.PRCo = HQCO.HQCo
WHERE     
    (dbo.PRTH.PREndDate BETWEEN '1/1/2012 00:00:00' AND '1/1/2013 00:00:00')
    AND (PRGroup = 2)
    AND dbo.PRTH.EarnCode IN (1,3,8)
GROUP BY 
    HQCO.HQCo, HQCO.Name, PREH.PRDept, PREH.Craft, 
    HRRM.PositionCode, PRTH.Employee, PREH.LastName, PREH.FirstName

But, I am trying to use an 'IN' predicate coupled with the CASE WHEN in the WHERE clause.. Have a look at the modified query below:

DECLARE @IncludePTO AS CHAR
SET @IncludePTO = 'Y'

SELECT     
   HQCO.HQCo, HQCO.Name, PREH.PRDept, PREH.Craft, HRRM.PositionCode, PRTH.Employee, 
   PREH.LastName, PREH.FirstName, SUM(PRTH.Hours) AS Hrs
FROM PREH 
INNER JOIN HRRM ON PREH.PRCo = HRRM.HRCo AND PREH.Employee = HRRM.HRRef 
INNER JOIN PRTH ON PREH.PRCo = PRTH.PRCo AND PREH.Employee = PRTH.Employee 
INNER JOIN HQCO ON PRTH.PRCo = HQCO.HQCo
WHERE     
    (dbo.PRTH.PREndDate BETWEEN '1/1/2012 00:00:00' AND '1/1/2013 00:00:00')
    AND (PRTH.PRGroup = 2)
    AND 
       CASE WHEN @IncludePTO = 'Y' THEN dbo.PRTH.EarnCode IN (1,2,3,8,100,110,120,115)
            ELSE dbo.PRTH.EarnCode IN (1,2,3,8)
       END
GROUP BY 
    HQCO.HQCo, HQCO.Name, PREH.PRDept, PREH.Craft, HRRM.PositionCode, PRTH.Employee, 
    PREH.LastName, PREH.FirstName

It doesn't seem to work and keeps giving me a syntax error:

Msg 156, Level 15, State 1, Line 15
Incorrect syntax near the keyword 'IN'.

Any help or guidance in pointing out what I'm missing? I would really appreciate any help/tips.. Thanks much,

Pranav

Answer 1

You are correct. The syntax is not allowed. You can try:

((@IncludePTO = 'Y' and dbo.PRTH.EarnCode IN (1,2,3,8,100,110,120,115)) or
 (@IncludePTO <> 'Y' and dbo.PRTH.EarnCode IN (1,2,3,8))
)

This can be simplified to:

(bo.PRTH.EarnCode IN (1,2,3,8) or (@IncludePTO <> 'Y' and dbo.PRTH.EarnCode IN (100,110,120,115))
)

This assumes that @IncludePTO is never NULL. If so, then that would have to be part of the test.

If you really want case statement in the where clause, you can do:

(CASE WHEN @IncludePTO = 'Y' and dbo.PRTH.EarnCode IN (1,2,3,8,100,110,120,115)
      then 'true'
      when @IncludePTO <> 'Y' and dbo.PRTH.EarnCode IN (1,2,3,8)
      then 'true'
      else 'false'
 end) = 'true'