SQL Server : check if variable is Empty or NULL for WHERE clause

Question

When searching for a list of products, the @SearchType parameter is optional. If @SearchType is empty or NULL then it should return al

Answer 1

If you can use some dynamic query, you can use LEN . It will give false on both empty and null string. By this way you can implement the option parameter.

ALTER PROCEDURE [dbo].[psProducts] 
(@SearchType varchar(50))
AS
BEGIN
    SET NOCOUNT ON;

DECLARE @Query nvarchar(max) = N'
    SELECT 
        P.[ProductId],
        P.[ProductName],
        P.[ProductPrice],
        P.[Type]
    FROM [Product] P'
    -- if @Searchtype is not null then use the where clause
    SET @Query = CASE WHEN LEN(@SearchType) > 0 THEN @Query + ' WHERE p.[Type] = ' + ''''+ @SearchType + '''' ELSE @Query END   

    EXECUTE sp_executesql @Query
    PRINT @Query
END