Problem in Where Clause

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Hello Everybody,

Problem in below query:

SQL

DECLARE @First_CName  VARCHAR(50)

SET @First_CName='Source_Id'

SELECT * FROM SourceDest_Details WHERE @First_CName =CAST(45 AS VARCHAR(50))--- This query is not working

But,

SQL

SELECT * FROM SourceDest_Details WHERE Source_Id=45-- This Query is Working

May i know the reason and if there is any possibility for first query to work

Posted 4-Apr-14 21:37pm

Member 10017719

Updated 4-Apr-14 21:52pm

Wendelius

v2

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3 solutions

Solution 2

You cannot dynamically change the structure of an SQL statement like that using variable contents.

If you need the statement to be dynamic, have a look at sp_executesql[^]

Posted 4-Apr-14 21:55pm

Wendelius

Comments

Member 10017719 5-Apr-14 4:10am

Ya I have tried with dynamic sql also as follows

SELECT TOP 1 @First_CName=COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME=@Table_Name

SET @From_Value=CAST(@fromId AS VARCHAR(50))
SET @To_Value=CAST(@toId AS VARCHAR(50))

SELECT @SQL='SELECT * FROM ' +@Table_Name+ ' WHERE '+ @First_CName +' BETWEEN CAST(' +@From_Value+' AS INT) AND CAST(' +@To_Value+ ' AS INT)'-- ex: @fromId=45 and @toId=46(inputs)

EXEC sp_executesql @SQL

Its returning error:The parameters supplied for the batch are not valid.

Wendelius 5-Apr-14 4:24am

When using dynamic SQL you have to concatenate the columns from the variables to the statement. For example:
...
SET @From_Value="CAST(" + @VarContainingColName + " AS VARCHAR(50))"
...

Solution 4

if you are supposed to use dynamic variables like @First_CName in where clause you have to surely use dynamic T_SQL

DECLARE @First_CName VARCHAR(50),
@lssql nvarchar(100)=''
SET @First_CName='Source_Id'
set @lssql='SELECT * FROM SourceDest_Details WHERE ('+@First_CName+'=CAST(''45'' AS VARCHAR(50)))'
print @lssql
execute sp_executesql @lssql

Posted 8-Apr-14 2:53am

Prakash Saminathan

Updated 8-Apr-14 3:07am

v2

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Schatak · Accepted Answer · 2014-04-04T22:37:00

Solution 3

try this

SQL

DECLARE @First_CName  VARCHAR(50)
SET @First_CName='Source_Id'
DECLARE @SQL varchar(1000)
SET @SQL = 'SELECT * FROM SourceDest_Details WHERE ('+@First_CName+'=CAST(''45'' AS VARCHAR(50)))'
EXEC(@SQL)

Posted 4-Apr-14 22:37pm

Schatak

Comments

Member 10017719 5-Apr-14 5:30am

Thank you Schatak...gr8

Schatak 5-Apr-14 5:35am

Your welcome :)

Er. Puneet Goel 5-Apr-14 7:14am

Whola!! Magical answer

Tom Marvolo Riddle 5-Apr-14 9:15am

Good one +5!

Schatak 8-Apr-14 8:55am

:)