在 SQL 中对包含数字的字符串列进行排序?
我正在尝试对字符串列(包含数字)进行排序.
I am trying to sort string column (containing numbers).
// SELECT `name` FROM `mytable` ORDER BY `name` ASC
+----------+
+-- name --+
+----------+
+-- a 1 ---+
+-- a 12 --+
+-- a 2 ---+
+-- a 3 ---+
你看到Mysql的自然排序算法在a 1之后放置a 12(这对大多数应用程序来说都可以)，但我有独特的需求，所以我希望结果应该这样排序.
You see natural sorting algorithm of Mysql is placing a 12 after a 1 (which is ok for most apps), But I have unique needs, so I want result should be sorted like this.
+----------+
+-- name --+
+----------+
+-- a 1 ---+
+-- a 2 ---+
+-- a 3 ---+
+-- a 12 --+
是否可以仅使用 SQL，或者我必须在应用程序级别操作结果集?
Is it possible with just SQL, or I have to manipulate result-set at application level?
推荐答案
继续假设它总是 WORD_space_NUMBER 这应该有效:
Going on the assumption it's always WORD_space_NUMBER this should work:
SELECT *
FROM table
ORDER BY CAST(SUBSTRING(column,LOCATE(' ',column)+1) AS SIGNED)
使用POSITION找到空间，SUBSTRING 抓取后面的数字，CAST 使其成为可比较的值.
Use POSITION to find the space, SUBSTRING to grab the number after it, and CAST to make it a comparable value.
如果该列有不同的模式，请告诉我，我会尝试设计出更好的解决方法.
If there is a different pattern to the column, let me know and I'll try to devise a better work-around.
编辑已证明有效:
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)
忽略我蹩脚的表/列名称，但给了我正确的结果.还更进一步，添加了双重排序以将字母前缀与数字分开.
ignore my lame table/column names, but gives me the correct result. Also went a little further and added double sort to break letters prefix with numeric.
编辑SUBSTRING_INDEX 将使它更具可读性.
ORDER BY SUBSTRING_INDEX(st, " ", 1) ASC, CAST(SUBSTRING_INDEX(st, " ", -1) AS SIGNED)
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