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。
// SELECT `name` FROM `mytable` ORDER BY `name` ASC+----------+
+-- name --+
+----------+
+-- a 1 ---+
+-- a 12 --+
+-- a 2 ---+
+-- a 3 ---+
您会看到Mysql的自然排序算法放在a 12
后面a 1
( 对于大多数应用程序来说都可以 ),但是我有独特的需求,因此我希望结果应该像这样排序。
+----------++-- name --+
+----------+
+-- a 1 ---+
+-- a 2 ---+
+-- a 3 ---+
+-- a 12 --+
是否可能,或者我必须在应用程序级别操纵结果集?
回答:
继续 假设 它始终为WORD_space_NUMBER,这应该可行:
SELECT *FROM table
ORDER BY CAST(SUBSTRING(column,LOCATE(' ',column)+1) AS SIGNED)
使用POSITION查找空间,使用SUBSTRING捕获其后的数字,然后使用CAST使其具有可比较的值。
如果该列有另一种模式,请告诉我,我将尝试设计一种更好的解决方法。
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,但会给我正确的结果。还走得更远,添加了双重排序功能,以数字打破字母前缀。
SUBSTRING_INDEX
将使其更具可读性。
ORDER BY SUBSTRING_INDEX(st, " ", 1) ASC, CAST(SUBSTRING_INDEX(st, " ", -1) AS SIGNED)
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