SQL where clause problem

Posted on 2013-12-20
Medium Priority
Last Modified: 2013-12-20

I have a parameter passed into a stored proc. If its a 0 I want a data less than a fixed date (called @YearEnd) and if its 1 I want data greater than @yearend

How do I do this, have been playing with case statements in the where clause, but getting a bit stuck.

Question by:Andy Green
LVL 34

Expert Comment

by:Brian Crowe
ID: 39732058
   CASE @parameter
      WHEN 0 THEN someDateColumn < @YearEnd
      ELSE someDateColumn > @YearEnd
LVL 25

Expert Comment

by:Lee Savidge
ID: 39732071
You can't in the way you want.

Either you do:

if @myparam = 0
-- select statement here with one where clause
-- a different select statement with another where clause

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of you use dynamic sql

declare @sql nvarchar(1000), @option nvarchar(1), @yearend datetime

select @yearend = getdate() -- example value

if @myparam = 0
  select @option = '<'
  select @option = '>'

select @sql = 'select * from mytable where myvar ' + @option + ' ' + @yearend

exec (@sql)

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Accepted Solution

QuinnDex earned 1000 total points
ID: 39732081
        parameter  = 0 and
             datecol < @yearend
           parameter   <> 0 and
             datecol > @yearend

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LVL 30

Expert Comment

by:Olaf Doschke
ID: 39732098
Is the query complicated? If not you could of course simply do

IF @param=0
  SELECT ... WHERE datefield<@yearend
  SELECT ... WHERE datefield>@yearend

The CASE solution is also possible and of course is more elegant, as you don't duplicate the query itself and don't have to maintain both queries and keep them in sync aside of the < or >.

But you can't put datefield>@yearend as a THEN or ELSE expression, you can compute two different expressions, which result in >0, eg:

SELECT.... WHERE CASE WHEN @passedinparam=0
    THEN datediff(d, datefield, @yearend)
    ELSE datediff(d, @yearend, datefield)
    END >0

You didn't specify the datefield name and the name if the parameter being 0 or 1, you can figure that out, I assume.

Bye, Olaf.
LVL 61

Assisted Solution

by:Kevin Cross
Kevin Cross earned 1000 total points
ID: 39732099
I agree with QuinnDex but note the first suggestion can be done like this:

      WHEN @parameter = 0 AND someDateColumn < @YearEnd THEN 1
      WHEN @parameter <> 0 AND someDateColumn > @YearEnd THEN 1
      ELSE 0
   END = 1

You will want to check the performance of the different solutions and pick what works best for you.

Author Closing Comment

by:Andy Green
ID: 39732150
Thanks Guys

I have split the points I went with QuinnDex in the first instance, it worked but I ran into problems with adding further parameters, I was able to do this easily with mwvisa's solution.

I know I didn't mention the other params in my OP but I didn't want to over complicate things

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