在SQL中对包含数字的字符串列进行排序？

Question

我正在尝试排序字符串列(包含数字).

// SELECT `name` FROM `mytable` ORDER BY `name` ASC
+----------+
+-- name --+
+----------+
+-- a 1 ---+
+-- a 12 --+
+-- a 2 ---+
+-- a 3 ---+

你看的Mysql的自然排序算法放置a 12后a 1(这是确定的大多数应用程序),但我有独特的需求,所以我想结果应该是这样排序.

+----------+
+-- name --+
+----------+
+-- a 1 ---+
+-- a 2 ---+
+-- a 3 ---+
+-- a 12 --+

是否可以只使用SQL,或者我必须在应用程序级别操作结果集？

Answer 1

继续假设它总是WORD_space_NUMBER这应该工作:

SELECT   *
FROM     table
ORDER BY CAST(SUBSTRING(column,LOCATE(' ',column)+1) AS SIGNED)

使用POSITION查找空格,使用SUBSTRING获取后面的数字,使用CAST使其成为可比较的值.

如果列中有不同的模式,请告诉我,我会尝试设计更好的解决方法.

编辑证明工作:

mysql> INSERT INTO t (st) VALUES ('a 1'),('a 12'),('a 6'),('a 11');
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM t ORDER BY st;
+----+------+
| id | st   |
+----+------+
|  1 | a 1  |
|  4 | a 11 |
|  2 | a 12 |
|  3 | a 6  |
+----+------+
4 rows in set (0.00 sec)

mysql> SELECT * FROM t ORDER BY CAST(SUBSTRING(st,LOCATE(' ',st)+1) AS SIGNED);
+----+------+
| id | st   |
+----+------+
|  1 | a 1  |
|  3 | a 6  |
|  4 | a 11 |
|  2 | a 12 |
+----+------+

mysql> INSERT INTO t (st) VALUES ('b 1'),('b 12'),('b 6'),('b 11');
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM t ORDER BY CAST(SUBSTRING(st,LOCATE(' ',st)+1) AS SIGNED);
+----+------+
| id | st   |
+----+------+
|  1 | a 1  |
|  5 | b 1  |
|  3 | a 6  |
|  7 | b 6  |
|  4 | a 11 |
|  8 | b 11 |
|  2 | a 12 |
|  6 | b 12 |
+----+------+
8 rows in set (0.00 sec)

mysql> SELECT * FROM t ORDER BY LEFT(st,LOCATE(' ',st)), CAST(SUBSTRING(st,LOCATE(' ',st)+1) AS SIGNED);
+----+------+
| id | st   |
+----+------+
|  1 | a 1  |
|  3 | a 6  |
|  4 | a 11 |
|  2 | a 12 |
|  5 | b 1  |
|  7 | b 6  |
|  8 | b 11 |
|  6 | b 12 |
+----+------+
8 rows in set (0.00 sec)

忽略我的蹩脚表/列名,但给我正确的结果.还进一步添加了双重排序来打破字母前缀与数字.

编辑 SUBSTRING_INDEX将使其更具可读性.

ORDER BY SUBSTRING_INDEX(st, " ", 1) ASC, CAST(SUBSTRING_INDEX(st, " ", -1) AS SIGNED)