Web Listing 2: Itzik’s Solution
WITH Nums(n) AS
(
            SELECT 1
  UNION ALL SELECT 2
  UNION ALL SELECT 3
  UNION ALL SELECT 4
  UNION ALL SELECT 5
  UNION ALL SELECT 6
  UNION ALL SELECT 7
  UNION ALL SELECT 8
),
Strings(string, strlen) AS
(
  SELECT CAST(n AS VARCHAR(8)), 1
  FROM Nums

  UNION ALL

  SELECT 
    CAST(PRV.string + CAST(NXT.n AS VARCHAR(1)) AS VARCHAR(8)),
    PRV.strlen + 1
  FROM Strings AS PRV
    JOIN Nums AS NXT
      ON PRV.strlen < 8
      AND PRV.string NOT LIKE '%' + CAST(NXT.N AS VARCHAR(1)) + '%'
      AND NOT EXISTS
        (SELECT * 
         FROM Nums AS D
         WHERE D.n <= PRV.strlen
           AND PRV.strlen + 1 - D.n =
             ABS(NXT.n - CAST(SUBSTRING(PRV.string, D.n, 1) AS INT)))
)
SELECT string
FROM Strings
WHERE strlen = 8 
ORDER BY string;