MySQL：在查詢中使用它之前對值進行排序

Question

在查詢中使用它之前，可以對值列表進行排序嗎？

贊SELECT SORTINGFN(2,3,1)並得到1,2,3？ 類似SELECT 2,3,1 ORDER BY ??? ASC，但按順序排序？

我需要確保的參數總是以相同的順序，從MD5('1,2,3')和MD5('2,3,1')

Answer 1

得到相同的哈希沒有表（設定值argx）：

SELECT arg1,arg2,arg3, 
    MD5(SELECT GROUP_CONCAT(col ORDER BY col) 
     FROM (SELECT arg1 AS col 
      UNION ALL SELECT arg2 
      UNION ALL SELECT arg3) AS sub) AS md5_checksum 

SqlFiddleDemo

輸出：

╔════╦════╦════╦══════════════════════════════════╗ 
║ 1 ║ 2 ║ 3 ║   md5_checksum   ║ 
╠════╬════╬════╬══════════════════════════════════╣ 
║ 1 ║ 2 ║ 3 ║ 55b84a9d317184fe61224bfb4a060fb0 ║ 
║ 3 ║ 2 ║ 1 ║ 55b84a9d317184fe61224bfb4a060fb0 ║ 
║ 3 ║ 1 ║ 2 ║ 55b84a9d317184fe61224bfb4a060fb0 ║ 
╚════╩════╩════╩══════════════════════════════════╝ 

無論如何MD5是弱散列算法。

---

SQL可以做很多事情。問題是這樣的操作的好地方，當你可以在應用層做到這一點。

任意列表：

SELECT MD5(GROUP_CONCAT(val ORDER BY val)) AS md5_sum 
FROM (
    SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(t.results, ',', n.n), ',', -1) AS val 
    FROM (SELECT '3,2,1,10,212,3123,1' AS results) AS t 
    CROSS JOIN 
    (
    SELECT a.N + b.N * 10 + 1 n 
     FROM 
     (SELECT 0 AS N UNION ALL 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 UNION ALL SELECT 9) a 
    ,(SELECT 0 AS N UNION ALL 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 UNION ALL SELECT 9) b 
) n 
    WHERE n.n <= 1 + (LENGTH(t.results) - LENGTH(REPLACE(t.results, ',', ''))) 
) sub 

SqlFiddleDemo2

輸出：

╔══════════════════════╦══════════════════════════════════╗ 
║  args   ║    md5_sum    ║ 
╠══════════════════════╬══════════════════════════════════╣ 
║ 3,2,1,10,212,3123,1 ║ e2003296ed64cb59be61558275e22433 ║ 
║ 212,3123,1,3,2,1,10 ║ e2003296ed64cb59be61558275e22433 ║ 
╚══════════════════════╩══════════════════════════════════╝