Sorting string column containing numbers in SQL?

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 ---+

You see natural sorting algorithm of Mysql is placing a 12 after a 1 (which is ok for most apps), But I have unique need开发者_运维百科s, so I want result should be sorted like this.

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

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

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)

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

If there is a different pattern to the column, let me know and I'll try to devise a better work-around.

EDIT Proven to work:

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)

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.

Edit SUBSTRING_INDEX will make it little more readable.

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

You can try this:

ORDER BY CASE
  WHEN ISNUMERIC(column) THEN cast(column as int) 
  else ascii(column[1,1]) 
end

Have a look at the MySQL CAST / Convert functions.

SELECT name FROM mytable ORDER BY CAST(name AS INTEGER) ASC;

Edit: I read:

I am trying to sort string column (containing numbers).

...but just took a look at the result set. Is the a actually also part of the contents? If so, you can use functions like MID to extract only the numeric value and cast that.

But if all rows contain just a without variation, you might as well omit it...

Another option could be to pad the string with spaces to the left of the number (i.e. add spaces between the word and the number) and use the resulting string for sorting, comething like this:

ORDER BY INSERT(
  column,
  LOCATE(' ', column),
  0,
  SPACES(20 - LENGTH(column) + LOCATE(' ', column))
)

The string is assumed to be of the pattern 'word followed by space(s) followed by number', and the number is assumed to be non-negative (or it would sort incorrectly). The hardcoded 20 is chosen arbitrarily and is supposed to be the string's number part's maximum possible length.

Here i found another solution with following query using Convert

select * from tablename where columnname like '%a%' order by Convert(smallint,Replace(columnname,'a',''))