Question

I have a table with following structure

Table name: matches

That basically stores which product is matching which product. I need to process this table
And store in a groups table like below.

Table Name: groups

group_ID stores the MIN Product_ID of the Product_IDS that form a group. To give an example let’s say

If A is matching B and B is Matching C then three rows should go to group table in format (A, A), (A, B), (A, C)

I have tried looking into co-related subqueries and CTE, but not getting this to implement.

I need to do this all in SQL.

Thanks for the help .

Answer 1

Try this:

;WITH CTE
AS
(
    SELECT DISTINCT
        M1.Product_ID Group_ID,
        M1.Product_ID
    FROM matches M1
        LEFT JOIN matches M2
            ON M1.Product_Id = M2.matching_Product_Id
    WHERE M2.matching_Product_Id IS NULL
    UNION ALL
    SELECT
        C.Group_ID,
        M.matching_Product_Id
    FROM CTE C
        JOIN matches M
            ON C.Product_ID = M.Product_ID
)
SELECT * FROM CTE ORDER BY Group_ID

You can use OPTION(MAXRECURSION n) to control recursion depth.

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