How Can a Recursive SQL Query Group Matching Products by Minimum Product ID?

Recursive Query in SQL Server

To retrieve matching products grouped by their minimum Product ID, a recursive query can be employed. This query iterates through a table, traversing the Product_ID relationships, and accumulating the results in a separate groups table. The recursive structure ensures that all matches are identified and included in the results.

Solution:

WITH CTE
AS
(
    SELECT DISTINCT
        M1.Product_ID AS 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

In this query, the CTE is a recursive definition that identifies the minimum Product_ID for each group. The query starts by selecting the Product_IDs that do not have a matching Product_Id, creating the initial groups. In the recursive step, the query joins the CTE with the matches table to identify matching Product_IDs and add them to the groups. This process continues until all matches are processed.

The final result is a table named groups that contains the MIN Product_ID for each group, along with all the Product_IDs that belong to that group. This structure enables efficient queries on product relationships and groupings.

Note:

To control the recursion depth, use the OPTION(MAXRECURSION n) clause, replacing n with the desired maximum recursion level.

Example: SQL Fiddle Demo

https://www.sqlfiddle.com/#!18/c772e/11

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