Question

Need help on how to improve my SQL script for better performance. dbo.Products table has a million rows. I’m hesitant to rewrite it using dynamic SQL. Thanks!

DECLARE
    @Brand varchar(MAX) = 'Brand 1, Brand 2, Brand 3',
    @ItemCategory varchar(MAX) = 'IC1, IC2, IC3, IC4, IC5'

--will return all records if params where set to @Brand = NULL, @ItemCategory = NULL

SELECT
     [Brand],
     SUM([Amount]) AS [Amount] 
FROM dbo.Products (NOLOCK)
LEFT JOIN [dbo].[Split](@Brand, ',') FilterBrand ON Brand = [FilterBrand].[Items]
LEFT JOIN [dbo].[Split](@ItemCategory, ',') FilterItemCategory ON ItemCategory = [FilterItemCategory].[Items] 
WHERE
    (@Brand IS NULL OR (@Brand IS NOT NULL AND [FilterBrand].[Items]  IS NOT NULL)) AND
    (@ItemCategory IS NULL OR (@ItemCategory IS NOT NULL AND [FilterItemCategory].[Items] IS NOT NULL))
GROUP BY
     [Brand]

Below is the split table-valued function that I found on the web:

CREATE function [dbo].[Split]
(
    @String     varchar(8000),
    @Delimiter  char(1)
)
RETURNS @Results TABLE (Items varchar(4000))
AS
BEGIN
    IF (@String IS NULL OR @String = '') RETURN

    DECLARE @i int, @j int

    SELECT @i = 1

    WHILE @i <= LEN(@String)
        BEGIN
            SELECT  @j = CHARINDEX(@Delimiter, @String, @i)

            IF @j = 0
                BEGIN
                    SELECT  @j = len(@String) + 1
                END

            INSERT  @Results SELECT RTRIM(SUBSTRING(@String, @i, @j - @i))

            SELECT  @i = @j + LEN(@Delimiter)
        END

    RETURN
END

Answer 1

Following solution are with out using functions

Declare @IDs Varchar(100)
SET @IDs = '2,4,6'

Select IsNull(STUFF((Select ', '+ CAST([Name] As Varchar(100)) From [TableName]
Where CharIndex(','+Convert(Varchar,[ID])+',', ','+@IDs+',')> 0
For XML Path('')),1,1,''),'') As [ColumnName]