Question

I have the following function:

CREATE FUNCTION [dbo].[ListStockBySubCategory]
(   
    @CategoryID varchar(10),
    @SubCategoryID  varchar(10),
    @startRowIndex  int,
    @maximumRows    int
)
RETURNS TABLE 
AS
RETURN 
(
SELECT ISBN FROM (
SELECT ISBN, 
ROW_NUMBER() OVER(AddedDate DESC) AS RowNum
FROM (
        SELECT DISTINCT RTRIM(LTRIM(CategoryCode)) + '%' AS Pattern
        FROM tblSubCategories
        WHERE SubCategoryID = @SubCategoryID) Cats
        JOIN tblStock Stock
        ON Stock.CategoryCode LIKE Cats.Pattern 
) AS Info
WHERE RowNum BETWEEN @startRowIndex AND (@startRowIndex + @maximumRows) - 1
)

Which thanks to help from others on StackOverflow, would list all the items with a Given SubCategory – however I want to be able to include the following:

    SELECT DISTINCT RTRIM(LTRIM(CategoryCode)) + '%' AS Pattern
    FROM tblCategories
    WHERE CategoryID = @CategoryID) Cats
    JOIN tblStock Stock
    ON Stock.CategoryCode LIKE Cats.Pattern

So that it gets the Categories as a Set, then the SubCategories is a SubSet of this, for example I have a Category of EG, which contains two SubCategories EG-EG and EG-IE which themselves are a List of category codes, for example:

EG-EG
– ETC
– ECT
– TCE
EG-IE
– EIEG
– EGIE

How to I get it so it does the Categories then from this List then does thr SubCategories, as part of this I need a “NOT” behaviour as there will be a General Category which will pick up all the left over SubCategories, that are not specifically stated, but would be picked up by the Category Query.

I just cannot find the right combination for this – SubCategories and Categories work seperately but I want them to be SuperSets and SubSets of each other.

---

Here is the the ListStockByCategoryFunction:

CREATE FUNCTION [dbo].[ListStockByCategory]
(   
    @CategoryID varchar(10),
    @startRowIndex  int,
    @maximumRows    int
)
RETURNS TABLE AS
RETURN
(
SELECT ISBN FROM (SELECT ISBN, 
ROW_NUMBER() OVER(ORDER BY AddedDate DESC) AS RowNum
FROM (
        SELECT DISTINCT RTRIM(LTRIM(CategoryCode)) + '%' AS Pattern
        FROM tblCategory
        WHERE CategoryID = @CategoryID) Cats
        JOIN tblStock Stock
        ON Stock.CategoryCode LIKE Cats.Pattern
) AS Info
WHERE RowNum BETWEEN @startRowIndex AND (@startRowIndex + @maximumRows) - 1
)

---

I have a Solution which works, however the performance is not acceptable, could anyone help with this as I have been working on it for some time and cannot seem to find a way to optimise this – the SubCategories are a SubSet of the Categories if this helps, see the example below:

CREATE FUNCTION [dbo].[ListStockBySubCategory]
(   
    @CategoryID     varchar(10),
    @SubCategoryID  varchar(10),
    @startRowIndex  int,
    @maximumRows    int
)
RETURNS TABLE 
AS
RETURN (
SELECT ISBN FROM (
SELECT ISBN,
ROW_NUMBER() OVER(ORDER BY AddedDate DESC) AS RowNum
FROM BooksInStock WHERE ISBN IN
(SELECT ISBN FROM(SELECT DISTINCT RTRIM(LTRIM(CategoryCode)) + '%' AS Pattern
        FROM tblCategories
        WHERE CategoryID = @CategoryID) Cats
        JOIN tblStock Stock
        ON Stock.CategoryCode LIKE Cats.Pattern
WHERE 
ISBN IN
(SELECT ISBN FROM(SELECT DISTINCT RTRIM(LTRIM(CategoryCode)) + '%' AS Pattern
        FROM tblSubCategories
        WHERE SubCategoryID = @SubCategoryID) Cats
        JOIN tblStock Stock
        ON Stock.CategoryCode LIKE Cats.Pattern))
) AS Info WHERE RowNum BETWEEN @startRowIndex AND (@startRowIndex + @maximumRows) - 1)

Answer 1

Well, its impossible to say without the table definitions, keys, indexes query plans or data examples, but I think that this will help some:

CREATE FUNCTION [dbo].[ListStockBySubCategory]
(   
    @CategoryID     varchar(10),
    @SubCategoryID  varchar(10),
    @startRowIndex  int,
    @maximumRows    int
)
RETURNS TABLE AS
RETURN 
(
    SELECT ISBN FROM 
    (
        SELECT  ISBN,  ROW_NUMBER() OVER(ORDER BY AddedDate DESC) AS RowNum
        FROM BooksInStock 
        WHERE EXISTS
        (        
            SELECT *

            FROM tblStock AS stk
            JOIN tblStock AS stk2         ON stk.ISBN = stk2.ISBN
            JOIN tblCategories AS cat     ON cat.CategoryID = @CategoryId
            JOIN tblSubCategories AS sub  ON cat.CategoryID = sub.CategoryID

            WHERE cat.CategoryID = @CategoryId
              AND sub.CategoryID = @CategoryId
              AND bis.ISBN = stk.ISBN
              AND  stk.CategoryCode LIKE RTRIM(LTRIM(cat.CategoryCode))+'%'
              AND stk2.CategoryCode LIKE RTRIM(LTRIM(sub.CategoryCode))+'%'
        )
    ) AS Info 
    WHERE RowNum BETWEEN @startRowIndex AND (@startRowIndex + @maximumRows) - 1
)