Database Challenges

--gustavo_gonzalez_tsqlchallenge_22.sql
DECLARE @result TABLE(BallId INT, BoxId INT);
DECLARE @total INT;
SET @total = 1;
WHILE (@total > 0)
BEGIN
INSERT INTO @result
SELECT
   p.BallId, MIN(p.BoxId)
FROM
   TC22_Preferences p
WHERE
     NOT EXISTS (SELECT 1 FROM @result WHERE NOT(BallId <> p.BallId AND BoxId <> p.BoxId))
GROUP BY
   p.BallId
HAVING COUNT(DISTINCT p.BoxId) = 1
UNION
SELECT
   MIN(p.BallId), p.BoxId
FROM
   TC22_Preferences p
WHERE
     NOT EXISTS (SELECT 1 FROM @result WHERE NOT(BallId <> p.BallId AND BoxId <> p.BoxId))
GROUP BY
   p.BoxId
HAVING COUNT(DISTINCT p.BallId) = 1
;
SET @total = @@ROWCOUNT;
END
SELECT 
   BoxName Box
 , BallName Ball
FROM
   @result t
   JOIN TC22_Boxes a ON t.BoxId = a.BoxId
   JOIN TC22_Balls b ON t.BallId = b.BallId
ORDER BY
   t.BoxId

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