在SQL中对包含数字的字符串列进行排序? [英] Sorting string column containing numbers in SQL?

问题描述

我正在尝试对字符串列(包含数字的 )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 ---+

您会看到Mysql的自然排序算法是将a 12放在a 1之后(对于大多数应用都是可以的)，但是我有独特的需求，所以我希望结果应该像这样排序

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 --+

仅使用SQL 是否可以，或者我必须在应用程序级别操纵结果集?

Is it possible with just SQL, or I have to manipulate result-set at application level?

推荐答案

继续进行假设，它总是WORD_space_NUMBER，应该可以:

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 来找到空格，SUBSTRING 抓取其后的数字，然后CAST 使其具有可比性.

Use POSITION to find the space, SUBSTRING to grab the number after it, and CAST to make it a comparable value.

如果该列有其他模式，请告诉我，我将尝试设计一种更好的解决方法.

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)

忽略我的la脚表/列名，但给我正确的结果.还走得更远，添加了双重排序功能，以数字分隔字母前缀.

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将使其更具可读性.

Edit SUBSTRING_INDEX will make it little more readable.

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

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