How to add if condition into the SELECT query

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Hi,

I have a stored procedure that return scalar value and I want to implement query like this:

SQL

SELECT @SUM = SUM(table1.id) FROM table1
IF (@param1 IS NOT NULL)
   INNER JOIN table2 ON table1.t2=table2.id
IF (@param2 IS NOT NULL)
   INNER JOIN table3 ON table1.t3=table3.id
WHERE IF (@param1 IS NOT NULL)
          table2.field=@field2
      IF (@param2 IS NOT NULL)
          AND table3.field=@field3

So how could I add these conditions into query?

Thanks in advance.

Posted 11-Sep-11 21:57pm

Salah_Afa

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3 solutions

Solution 3

Use a Dynamic Sql

SQL

declare @strSql nvarchar(1000) 
declare @param1 nvarchar(10) = ''
declare @param2 nvarchar(10) = ''
set @strSql = 'SELECT @SUM = SUM(table1.id) FROM table1 ' 
IF (@param1 IS NOT NULL)
   set @strSql = @strSql + ' INNER JOIN table2 ON table1.t2=table2.id'
IF (@param2 IS NOT NULL)
   set @strSql = @strSql +' INNER JOIN table3 ON table1.t3=table3.id'
set @strSql = @strSql +' WHERE '
IF (@param1 IS NOT NULL)
          set @strSql = @strSql +' table2.field=@field2'
      IF (@param2 IS NOT NULL)
          set @strSql = @strSql +' AND table3.field=@field3'

print @strSql 
exec sp_executesql @strSql

Posted 12-Sep-11 1:47am

sachin10d

Comments

[no name] 12-Sep-11 8:22am

good one

Salah_Afa 12-Sep-11 10:47am

I tried your solution, but this message appeared:
Must declare the scalar variable "@Sum".

But I declare @Sum before the dynamic sql.
????

sachin10d 12-Sep-11 23:49pm

change the strSql statment as
set @strSql = ' declare @sum int '
set @strSql = @strSql + 'SELECT @SUM = SUM(table1.id) FROM table1 '

Salah_Afa 13-Sep-11 3:23am

It also didn't work. But I noticed in the debugging mode that the @strSql didn't contain all the text that I set them to it.
So do you have any explanation???

Solution 2

Hi,

the simple solution is that you need to write two sql queries 1 for param1 is not null and another for param2 is not null and combine the result using UNION AL keyword

Posted 11-Sep-11 22:32pm

MaulikDusara

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Prerak Patel · Accepted Answer · 2011-09-11T22:11:00

Solution 1

http://stackoverflow.com/questions/317377/sql-if-statement-in-where-clause-for-searching-database[^]
http://stackoverflow.com/questions/87821/sql-if-clause-within-where-clause[^]

Posted 11-Sep-11 22:11pm

Prerak Patel

Updated 11-Sep-11 22:12pm

v2