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If Then Else in WHERE Clause

Posted on 2006-11-06
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Last Modified: 2008-02-01
I would like to pass a string parameter into a stored procedure that will do the following

@param1 int
@Assignment nvarchar(12)

Select blah blah blah subquery1 as blah1, subquery 2 as blah2.... (Long drawn out select query)  from Table1 WHERE
Division = @param1 AND ....


if @Assignment = 'Unassigned' then the where clause should be AssignedTo = '-1'
if @Assignment = 'Assigned' then the where clause should be AssignedTo <> '-1'
if @Assignment = 'All' then skip this part of the where clause.

Thanks in advance.

Dan
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Question by:DigitalDan3
3 Comments
 
LVL 143

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 668 total points
ID: 17882164
@param1 int
@Assignment nvarchar(12)

Select blah blah blah subquery1 as blah1, subquery 2 as blah2.... (Long drawn out select query)  
FROM Table1
WHERE Division = @param1
AND (
            ( @Assignment = 'Unassigned' AND AssignedTo = '-1' )
       OR ( @Assignment = 'Assigned' AND AssignedTo <> '-1' )
       OR ( @Assignment = 'All' )
     )

0
 
LVL 75

Assisted Solution

by:Aneesh Retnakaran
Aneesh Retnakaran earned 668 total points
ID: 17882177
Select blah blah blah subquery1 as blah1, subquery 2 as blah2.... (Long drawn out select query)  from Table1 WHERE
Division = @param1 AND (
(@Assignment = 'Unassigned' AND AssignedTo = '-1' )
OR
(@Assignment = 'Assigned'  AND AssignedTo <> '-1')
OR
( @Assignment = 'All'  AND 1 =1 )
)
0
 
LVL 29

Accepted Solution

by:
Nightman earned 664 total points
ID: 17882227
While both of those posted may work (and are more convenient given the code reusability), it would execute faster to do it like this:

Create procedure MyProcedure
(
@param1 int
@Assignment nvarchar(12)
)
as
if @Assignment='Unassigned'
begin
  Select blah blah blah subquery1 as blah1, subquery 2 as blah2.... (Long drawn out select query)  from Table1 WHERE Division = @param1 AND AssignedTo = '-1'
end
else if @Assignment='Assigned'
begin
  Select blah blah blah subquery1 as blah1, subquery 2 as blah2.... (Long drawn out select query)  from Table1 WHERE Division = @param1 AND AssignedTo <> '-1'
end
else if @Assignment = 'All'
begin
  Select blah blah blah subquery1 as blah1, subquery 2 as blah2.... (Long drawn out select query)  from Table1 WHERE Division = @param1
end

In fact, to make it even faster (and allow SQL to cache a seperate and most likely optimal query plan for each permutation) it would be even better to have a stored procedure for EACH permutation, and have your primary procedure call each one internally based on the value of assignment.

More work, but avoids recompiles and re-use of potentially inefficient query plans.
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