SQL performance on ROWCOUNT check - better way? - sql

Question

I have a MS SQL 2005 stored procedure that I pass an ID to from a web page.
The ID is used to read pre-set search criteria from a database of widget category landing pages into a set of variables.
The variables are then used in a SELECT to search a database of widget items. Some variables can be overridden by a visitor's page choices, such as maximum price.
I'd like to check if the SELECT returns records, and, if not, default to the landing page's normal criteria to make sure the visitor always sees some items.
I have tried using ##ROWCOUNT to check the first SELECT but, as the SELECT is fairly involved (I've taken out a lot of fields in the example below), the performance hit of running it twice is unacceptably long. The first SELECT on its own takes around 1 second, whereas checking for ##ROWCOUNT = 0 and running the SELECT again takes around 4 seconds.
Is there a better way to accomplish this check and return of records if the first SELECT returns none?
I also want to return only one recordset, not two, at the end of the stored procedure.
Having researched this, I have found people using UNION ALL on two selects, but I don't think it helps me in this case. I also want to know which SELECT was used by passing through a field with contents True or False, so I can flag up on the website whether no records have been found.
Thanks for your help.
CREATE PROCEDURE dbo.NW_LANDING_GET_Widgets
/* options from the web page */
#WidgetID int,
#PageNumber int,
#WidgetsPerPage int,
#Sort VARCHAR(1),
#MinPrice int,
#MaxPrice int,
#Override_WidgetType varchar(20),
#Override_WidgetInfo1 int
AS
SET NOCOUNT ON
BEGIN
/* ---------- Declare variables for criteria to be gathered from WidgetLanding table ------------ */
DECLARE #WidgetCategory1 varchar(50)
DECLARE #WidgetCategory2 varchar(50)
DECLARE #WidgetType varchar(30)
DECLARE #WidgetInfo1 int
/* ---------- Read default criteria into variables from WidgetLanding table ----- */
SELECT
#WidgetCategory1=Criteria_WidgetCategory1,
#WidgetCategory2=Criteria_WidgetCategory2,
#WidgetType=Criteria_WidgetType
FROM dbo.WidgetLanding
WHERE pk_WidgetID = #WidgetID
/* -------- Set PageNumber variable for SELECT of Widgets ----------- */
SET #PageNumber=(#PageNumber-1)*#WidgetsPerPage
/* Set Minimum and Maximum Prices - if Null, set highest and lowest number possible */
DECLARE #Min int
DECLARE #Max int
SET #Min = ISNULL(#MinPrice,0)
SET #Max = ISNULL(#MaxPrice,999999999)
/* -------- Override variables if visitor has changed the search criteria from default ------------------- */
IF #Override_WidgetType is not null
BEGIN
SET #WidgetType=#Override_WidgetType
END
IF #Override_WidgetInfo1 is not null
BEGIN
SET #WidgetInfo1=#Override_WidgetInfo1
END
/* ------------------- Retrieve widget records based on variables ------ */
SELECT TOP(#WidgetsPerPage) * FROM (SELECT RowID=ROW_NUMBER()
OVER (ORDER BY
CASE WHEN dbo.Widgets.Featured_WidgetLandingID = #WidgetID then 1 else 0 end DESC,
CASE WHEN #Sort = 'D' THEN dbo.Widgets.Price END DESC, /* Price Descending */
CASE WHEN #Sort = 'U' THEN dbo.Widgets.Price END ASC, /* Price Ascending */
CASE WHEN #Sort = 'P' THEN dbo.Widgets.viewed END DESC, /* Popular */
CASE WHEN #Sort = 'L' THEN dbo.Widgets.Date END DESC), /* Latest */
Count(dbo.Widgets.WidgetID) OVER() As TotalRecords,
dbo.Widgets.Price,
dbo.Widgets.WidgetID,
dbo.Widgets.WidgetCategory1,
dbo.Widgets.WidgetCategory2,
dbo.Widgets.WidgetType,
dbo.Widgets.WidgetType2,
dbo.Widgets.WidgetInfo1
FROM dbo.Widgets
WHERE
(WidgetCategory1 = #WidgetCategory1 OR #WidgetCategory1 is null) AND
(WidgetCategory2 = #WidgetCategory2 OR #WidgetCategory2 is null) AND
(Price >= #Min AND Price <= #Max) AND
(WidgetInfo1 >= #WidgetInfo1 OR #WidgetInfo1 is null)
) TAB WHERE TAB.RowId > CAST(#PageNumber AS INT)
/*
-----------------------------
THIS IS WHERE I WANT TO CHECK IF RECORDS ARE RETURNED - IF NOT DO ANOTHER SELECT BUT WITHOUT OVERRIDING VARIABLES SO RECORDS WILL ALWAYS BE RETURNED
-----------------------------
*/
END
SET NOCOUNT OFF

Answer 1

Simpliest way is code like this:
SELECT TOP(#WidgetsPerPage) *
INTO #Res
FROM (SELECT RowID=ROW_NUMBER()
OVER (ORDER BY
CASE WHEN dbo.Widgets.Featured_WidgetLandingID = #WidgetID then 1 else 0 end DESC,
CASE WHEN #Sort = 'D' THEN dbo.Widgets.Price END DESC, /* Price Descending */
CASE WHEN #Sort = 'U' THEN dbo.Widgets.Price END ASC, /* Price Ascending */
CASE WHEN #Sort = 'P' THEN dbo.Widgets.viewed END DESC, /* Popular */
CASE WHEN #Sort = 'L' THEN dbo.Widgets.Date END DESC), /* Latest */
Count(dbo.Widgets.WidgetID) OVER() As TotalRecords,
dbo.Widgets.Price,
dbo.Widgets.WidgetID,
dbo.Widgets.WidgetCategory1,
dbo.Widgets.WidgetCategory2,
dbo.Widgets.WidgetType,
dbo.Widgets.WidgetType2,
dbo.Widgets.WidgetInfo1
FROM dbo.Widgets
WHERE
(WidgetCategory1 = #WidgetCategory1 OR #WidgetCategory1 is null) AND
(WidgetCategory2 = #WidgetCategory2 OR #WidgetCategory2 is null) AND
(Price >= #Min AND Price <= #Max) AND
(WidgetInfo1 >= #WidgetInfo1 OR #WidgetInfo1 is null)
) TAB WHERE TAB.RowId > CAST(#PageNumber AS INT)
IF (##ROWCOUNT>0)
BEGIN
INSERT #Res (......)
SELECT
END
SELECT * FROM #Res
But anyway your query should be rewritten.