Stored procedure inserting values into a table using Table-Valued Parameters - sql-server

Question

Given the following simple structure:
TABLE: Product (ProductId, ProductName)
TABLE: Category (CategoryId, CategoryName)
LINK TABLE: ProductId,CategoryId
I have a table type which I want to pass to a stored procedure to insert the values into another table if they don't exist.
CREATE TYPE StringList_TBLType AS TABLE (s NVARCHAR(255) NOT NULL PRIMARY KEY)
I want to do the following in a stored procedure where I pass in a ProductName, and the StringList_TBLType of Category Names
select all the strings from my StringList_TBLType
Insert the string into the Category TABLE if it does not exist
Get the ID of the inserted or already existing Category
Insert the ProductId, and CategoryId into the LINK TABLE.
I could probably struggle along and get something working, but I have little experience with MS SQL, and stored procedures in general, and am scared that I would end up writing a very inefficient way of doing this.

Answer 1

You can use the MERGE statement to capture the category IDs.
DECLARE #changes TABLE (ChangeID VARCHAR(10), Id INTEGER);
DECLARE #JustSomeRandomVariable INT;
MERGE Category AS TARGET
USING #data AS SOURCE
ON TARGET.Category = SOURCE.s
WHEN NOT MATCHED THEN
INSERT ([Category])
VALUES (SOURCE.s)
WHEN MATCHED THEN
UPDATE SET #JustSomeRandomVariable = 1
OUTPUT $action, inserted.Id INTO #changes;
The random variable in the merge statement makes sure that updates get logged into the #changes table variable.
Now you can use the #changes to update your link table.
INSERT INTO Link SELECT ProductID, ChangeID FROM #changes
Just retrieve the required ProductID with a simple select query.
EDIT:
This could potentially result in double records in the Link table. You might need to tweak it a bit, perhaps use the MERGE statement for inserting into the Link table aswell.
#data is the StringList_TBLType paramter of your procedure.

Answer 2

This is what I would suggest (not tested)
CREATE PROCEDURE AddProductToCategories
#productname nvarchar(255),
#categories StringList_TBLType READONLY
AS
BEGIN
DECLARE #productId bigint --change to datatype of Product.ProductId
SET #productId = (SELECT TOP 1 ProductId FROM Product WHERE ProductName = #productname) --What to do if your product names are not unique?
IF #productId is not NULL
BEGIN
DECLARE cur CURSOR FOR (
SELECT cat.CategoryName, cat.CategoryId, c.s
FROM #categories c
RIGHT OUTER JOIN Category cat on c.s = cat.CategoryName
)
DECLARE #id as bigint --change to datatype of Category.CategoryId
DECLARE #name as nvarchar(255) --change to datatype of Category.CategoryName
DECLARE #categoryNameToAdd as nvarchar(255)
OPEN cur
FETCH NEXT FROM cur INTO #name, #id, #categoryNameToAdd
WHILE ##FETCH_STATUS = 0
BEGIN
IF #id is NULL
BEGIN
--category does not exist yet in table Category
INSERT INTO Category (CategoryName) VALUES (#categoryNameToAdd)
SET #id = SCOPE_IDENTITY()
END
INSERT INTO ProductsCategories --your link table
(ProductId, CategoryId)
VALUES
(#productId, #id)
FETCH NEXT FROM cur INTO #name, #id, #categoryNameToAdd
END --cursor
CLOSE cur
DEALLOCATE cur
END --IF #productId
END --sproc