How Can Recursive SQL Queries Group Product Matches Based on Minimum Product ID?

Recursive Querying in SQL Server

A data analyst encounters difficulty in transforming a table containing product matches into a desired grouping table. The aim is to derive a new table, named 'groups,' where each group is represented by the minimum product ID of its constituent products.

To achieve this, we can leverage SQL's recursive capabilities. Here is a solution using a common table expression (CTE):

;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

The CTE defines a recursive query starting with rows that do not have any matching products. Subsequently, it identifies additional matching products and groups them based on the minimum product ID. The recursion depth can be controlled using the OPTION(MAXRECURSION) clause.

This solution effectively aggregates product matches into groups as per the specified criteria.

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