Анатолий Слабоденюк

SELECT * 
  FROM @Words AS Wrd
    JOIN ( SELECT LEFT( Word1, 4 ) AS Word4
             FROM @Words
             GROUP BY LEFT( Word1, 4 )
             HAVING COUNT(*) > 1 ) AS Wrd4
      ON Wrd4.Word4 = LEFT( Word1, 4 )
    JOIN ( SELECT LEFT( Word2, 2 ) AS Word2
             FROM @Words
             GROUP BY LEFT( Word2, 2 )
             HAVING COUNT(*) > 1 ) AS Wrd2
      ON Wrd2.Word2 = LEFT( Wrd.Word2, 2 )

Решение задачи с усечённым столбцом. Переписать на MySQL, добавив подзапрос для второго столбца.