How to Check Parameter is not null in sql server? - sql

Question

I have a stored procedure. In this stored procedure I have to check that a particular parameter is not null. How can I do this? I wrote this:
ALTER PROCEDURE [dbo].[GetReelListings]
#locationUrlIdentifier VARCHAR(100)
AS
BEGIN
SET NOCOUNT ON;
declare #Sql varchar(max)=''
SET #Sql = 'SELECT CategoryName, CategoryUrlIdentifier, LocationUrlIdentifier, Directory.* FROM (SELECT ROW_NUMBER() OVER (PARTITION BY Category.Name ORDER BY CASE WHEN '''+ #locationUrlIdentifier + ''' = Location.UrlIdentifier THEN 1 ELSE CASE WHEN ''' + #locationUrlIdentifier + ''' IS NULL AND Directory.LocationId IS NULL THEN 0 ELSE 2 END END, Directory.SortOrder ) AS ''RowNo'', Category.Name AS CategoryName, Category.UrlIdentifier AS CategoryUrlIdentifier, dbo.Location.UrlIdentifier AS LocationUrlIdentifier, Directory.DirectoryId, CASE WHEN ''' + #locationUrlIdentifier + ''' = Location.UrlIdentifier THEN 1 ELSE CASE WHEN ''' + #locationUrlIdentifier + ''' IS NULL AND Directory.LocationId IS NULL THEN 0 ELSE 2 END END AS CategoryOrder FROM dbo.Directory INNER JOIN dbo.Category ON Directory.CategoryId = Category.CategoryId LEFT OUTER JOIN dbo.Location ON dbo.Directory.LocationId = location.Location_ID ) AS content INNER JOIN dbo.Directory ON content.DirectoryId = Directory.DirectoryId WHERE content.RowNo =1 '
if (#locationUrlIdentifier is null)
begin
SET #Sql = #Sql + ' and 1=1'
end
else
begin
SET #Sql = #Sql + ' and CategoryOrder = 1 '
end
print #SQl
EXECUTE (#Sql)
END
This will work in SQL but this will return a null Dataset in Codebehind.

Answer 1

Whenever you join strings and NULLs together, the result is NULL. By the time you're asking about whether the variable is NULL, you've already done this:
' + #locationUrlIdentifier + '
Several times. If it's NULL, so will #Sql be.
You might want to consider using COALESCE to replace the NULL with a suitable replacement (e.g. an empty string):
' + COALESCE(#locationUrlIdentifier,'') + '
You also still have a logic error on your final construction. If the variable is NULL, you'll have a where clause saying:
WHERE content.RowNo =1 1=1
Which isn't valid. I don't think you should be appending anything.
I'm also not clear on why you're doing this as dynamic SQL. The below seems to be an equivalent query which can be executed directly:
SELECT
CategoryName,
CategoryUrlIdentifier,
LocationUrlIdentifier,
Directory.*
FROM
(SELECT
ROW_NUMBER() OVER (
PARTITION BY Category.Name ORDER BY
CASE
WHEN #locationUrlIdentifier = Location.UrlIdentifier THEN 1
WHEN #locationUrlIdentifier IS NULL AND Directory.LocationId IS NULL THEN 0
ELSE 2
END,
Directory.SortOrder
) AS RowNo,
Category.Name AS CategoryName,
Category.UrlIdentifier AS CategoryUrlIdentifier,
dbo.Location.UrlIdentifier AS LocationUrlIdentifier,
Directory.DirectoryId,
CASE
WHEN #locationUrlIdentifier = Location.UrlIdentifier THEN 1
WHEN #locationUrlIdentifier IS NULL AND Directory.LocationId IS NULL THEN 0
ELSE 2
END AS CategoryOrder
FROM
dbo.Directory
INNER JOIN
dbo.Category
ON
Directory.CategoryId = Category.CategoryId
LEFT OUTER JOIN
dbo.Location
ON
dbo.Directory.LocationId = location.Location_ID
) AS content
INNER JOIN
dbo.Directory
ON
content.DirectoryId = Directory.DirectoryId
WHERE
content.RowNo =1 and
(#locationUrlIdentifier or CategoryOrder = 1)

Answer 2

You can do it just in ONE query:
Select Query ...where ...
and ((#locationUrlIdentifier is null) or (CategoryOrder = 1))

Answer 3

You can use NULLIF instead of IS NULL
Refer : Check if a parameter is null or empty in a stored procedure
http://msdn.microsoft.com/en-us/library/ms177562.aspx

Answer 4

Alternatively you can use ISNULL() check and then change the null to empty string
IF (ISNULL(#locationUrlIdentifier,'') = '')
OR even before this check you can use ISNULL() to convert from NULL to empty string if it persists to be a problem