mysql - 如何在Mysql中通过破折号反转字符串

Question

我得到的位置结果如下:

10-12-1

并希望得到这样的结果:

1-12-10

我正在应用字符串函数 REVERSE() 而不是结果

query  :  select REVERSE("10-12-1")
result : 1-21-01

我该如何解决？

Answer 1

您可以使用简单的技巧将其与 SUBSTRING_INDEX 和 GROUP_CONCAT 解析回一个字符串:

SELECT id, col, GROUP_CONCAT(val ORDER BY n DESC SEPARATOR '-') AS reversed
FROM
(
SELECT id, col,  SUBSTRING_INDEX(SUBSTRING_INDEX(t.col, '-', n.n), '-', -1) AS val, n
FROM tab 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.col) - LENGTH(REPLACE(t.col, '-', '')))
) sub
GROUP BY id

SqlFiddleDemo

输出:

╔═════╦═════════════════╦════════════════╗
║ id  ║      col        ║    reversed    ║
╠═════╬═════════════════╬════════════════╣
║  1  ║ 1-12-10         ║ 10-12-1        ║
║  2  ║ 111-12-10       ║ 10-12-111      ║
║  3  ║ 11123-2-103223  ║ 103223-2-11123 ║
╚═════╩═════════════════╩════════════════╝

请记住，此解决方案适用于 3 个以上的可变长度部分 (1-20-300-4000-500000-600000-7)。