MySql order by 排序

order by: 对所取得的数据按给定的字段今夕排序。

排序方式有：

正序 asc
倒序 desc
省略不写，默认 asc

可以单个排序
select * from test order by age asc;
select * from test order by age desc;
也可以多个排序，根据情况去使用
select * from test order by age asc, name desc;

测试数据

mysql> select * from test;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | dzm  |   20 |
|  2 | xyq  |   20 |
|  3 | xyq  |   20 |
|  4 | djy  |    5 |
|  5 | NULL | NULL |
+----+------+------+

mysql> select * from test order by age;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | NULL | NULL |
|  4 | djy  |    5 |
|  1 | dzm  |   20 |
|  2 | xyq  |   20 |
|  3 | xyq  |   20 |
+----+------+------+
5 rows in set (0.00 sec)

mysql> select * from test order by age asc;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | NULL | NULL |
|  4 | djy  |    5 |
|  1 | dzm  |   20 |
|  2 | xyq  |   20 |
|  3 | xyq  |   20 |
+----+------+------+
5 rows in set (0.00 sec)

mysql> select * from test order by age desc;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | dzm  |   20 |
|  2 | xyq  |   20 |
|  3 | xyq  |   20 |
|  4 | djy  |    5 |
|  5 | NULL | NULL |
+----+------+------+
5 rows in set (0.00 sec)

mysql> select * from test group by name;
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | NULL | NULL |
|  4 | djy  |    5 |
|  1 | dzm  |   20 |
|  2 | xyq  |   20 |
+----+------+------+
4 rows in set (0.00 sec)

mysql> select * from test group by name order by age desc;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | dzm  |   20 |
|  2 | xyq  |   20 |
|  4 | djy  |    5 |
|  5 | NULL | NULL |
+----+------+------+
4 rows in set (0.00 sec)