Help in creating T-SQL where clause

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Help in creating T-SQL where clause

PradeepVallabh

SSC Eights!

Points: 987
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February 19, 2013 at 4:52 pm

#274294

My front end aspx web page has a form with some text boxes, dropdown, radiobuttons, Datagrid and searchbutton. I need to populate Datagrid based upon the result set from searchbutton click event....Now the problem is not all the textboxes, dropdown's and radiobutton are required fields...Query for the searchbutton click event depends upon the search parameters provided by the user...
I am trying to figure out where condition for the query, but my query is becoming more and more complex as i have to check everytime whether each and every search parameter exists and write sql accordingly
PS: I have 8 different parameters for the form and only 2 parameters are required fields
Is there any better way of handling this issue?

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Kevin.roberts25 SSC Journeyman Points: 94 More actions · Answer 1

Try this which I got from code project, its a great way to do a query from a form with multiple parameters

Create Procedure sp_EmployeeSelect_Coalesce

@EmployeeName NVarchar(100),

@Department NVarchar(50),

@Designation NVarchar(50),

@StartDate DateTime,

@EndDate DateTime,

@Salary Decimal(10,2)

AS

Set NoCount ON

Select * From tblEmployees

where EmployeeName = Coalesce(@EmployeeName, EmployeeName) AND

Department = Coalesce(@Department, Department ) AND

Designation = Coalesce(@Designation, Designation) AND

JoiningDate >= Coalesce(@StartDate, JoiningDate) AND

JoiningDate <= Coalesce(@EndDate, JoiningDate) AND

Salary >= Coalesce(@Salary, Salary)

If @@ERROR <> 0 GoTo ErrorHandler

Set NoCount OFF

Return(0)

ErrorHandler:

Return(@@ERROR)

GO

Jeff Moden SSC Guru Points: 1004289 More actions · Answer 2

Kevin.roberts25 (2/19/2013)
Try this which I got from code project, its a great way to do a query from a form with multiple parameters
Create Procedure sp_EmployeeSelect_Coalesce
@EmployeeName NVarchar(100),
@Department NVarchar(50),
@Designation NVarchar(50),
@StartDate DateTime,
@EndDate DateTime,
@Salary Decimal(10,2)
AS
Set NoCount ON
Select * From tblEmployees
where EmployeeName = Coalesce(@EmployeeName, EmployeeName) AND
Department = Coalesce(@Department, Department ) AND
Designation = Coalesce(@Designation, Designation) AND
JoiningDate >= Coalesce(@StartDate, JoiningDate) AND
JoiningDate <= Coalesce(@EndDate, JoiningDate) AND
Salary >= Coalesce(@Salary, Salary)
If @@ERROR <> 0 GoTo ErrorHandler
Set NoCount OFF
Return(0)
ErrorHandler:
Return(@@ERROR)
GO

Kevin,

First, I know this isn't your fault and I'm not slamming you. You found what you think is a good article or post.

Have you got a link for that reference? I ask because I'd like to go there and set those folks straight on how bad this form of "Catch All" query can be since INDEX SCANS are virtually the only thing guaranteed to happen here.

The correct way to do this is with properly written, SQL-Injection-proof code. Please see the following article on one method for how easily this is accomplished.

http://sqlinthewild.co.za/index.php/2009/03/19/catch-all-queries/

Also, the use of GOTO has fallen out of favor with most people. TRY/CATCH seems to be the way to go now for most things.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Kevin.roberts25 SSC Journeyman Points: 94 More actions · Answer 3

sure here's the link, I dont use the whole thing I just found the use of the Coalesce statement interesting as i normally use where (columnName is null) or ( columnName =@columnName )

Code project Article Link

PradeepVallabh SSC Eights! Points: 987 More actions · Answer 4

Coalesce is something which doesn't give me the desired results....All i am trying to do is, if the parameter is not passed from UI i need to remove the parameter from where clause of sql Stored procedure ....

I guess probably the only way to handle this is to separate out the query and where clause(in Stored procedure) and use sp_executesql finally(which i hate doing it as i have to check everytime where the parameter is not null)

Anyother suggestions or thoughts???

brad.mason5 Hall of Fame Points: 3299 More actions · Answer 5

I attended a training by Itzik Ben Gan and we found that this technique worked the best for our data set.

-- Stored Procedure GetOrders,

-- Using Dynamic SQL

ALTER PROC dbo.GetOrders

@orderid AS INT = NULL,

@custid AS INT = NULL,

@empid AS INT = NULL,

@orderdate AS DATETIME = NULL

AS

DECLARE @sql AS NVARCHAR(1000);

SET @sql =

N'SELECT orderid, custid, empid, orderdate, filler /* 27702431-107C-478C-8157-6DFCECC148DD */'

+ N' FROM dbo.Orders'

+ N' WHERE 1 = 1'

+ CASE WHEN @orderid IS NOT NULL THEN

N' AND orderid = @oid' ELSE N'' END

+ CASE WHEN @custid IS NOT NULL THEN

N' AND custid = @cid' ELSE N'' END

+ CASE WHEN @empid IS NOT NULL THEN

N' AND empid = @eid' ELSE N'' END

+ CASE WHEN @orderdate IS NOT NULL THEN

N' AND orderdate = @dt' ELSE N'' END;

EXEC sp_executesql

@stmt = @sql,

@params = N'@oid AS INT, @cid AS INT, @eid AS INT, @dt AS DATETIME',

@oid = @orderid,

@cid = @custid,

@eid = @empid,

@dt = @orderdate;