如果表字段的类型为varchar型，但是里面存储的是纯数字，怎么实现按照数字的大小来排序？
下面的方法对于mysql和oracle都实用
order by 字段+0
order by 字段*1
等等都可以实现

例子：
Mysql：
mysql> select * from goolen;
+------+
| id   |
+------+
| 1    |
| 2    |
| 3    |
| 4    |
| 5    |
| 10   |
| 11   |
| 20   |
| 22   |
+------+
9 rows in set (0.00 sec)

mysql> select * from goolen order by id;
+------+
| id   |
+------+
| 1    |
| 10   |
| 11   |
| 2    |
| 20   |
| 22   |
| 3    |
| 4    |
| 5    |
+------+
9 rows in set (0.00 sec)

mysql> select * from goolen order by id+0;
+------+
| id   |
+------+
| 1    |
| 2    |
| 3    |
| 4    |
| 5    |
| 10   |
| 11   |
| 20   |
| 22   |
+------+
9 rows in set (0.00 sec)

Oracle：
SQL> select * from goolen;

ID
------------------------------
20
44
28
15
29
3
25
39
51
26

10 rows selected.

SQL> select * from goolen order by id;

ID
------------------------------
15
20
25
26
28
29
3
39
44
51

10 rows selected.

SQL> select * from goolen order by id+0;

ID
------------------------------
3
15
20
25
26
28
29
39
44
51

10 rows selected.

SQL> select * from goolen order by id*1;

ID
------------------------------
3
15
20
25
26
28
29
39
44
51

10 rows selected.