order by 1 是什么意思

• ORDER BY 1

ORDER BY 1 表示按select的第一个字段排序 

mysql> select id,name from employee
    -> order by 1;

在这个例子中就是以 id 字段来排序。

• ORDER BY n

ORDER BY n 表示，以“第n个字段”排序。
可在n的后面加 升序 ASC 降序 DESC 关键字。

例子，

mysql> SELECT * FROM employee ORDER BY 1 ASC;
+----+-------+---------+
| id | name  | address |
+----+-------+---------+
|  1 | carol | japan   |
|  2 | bob   | tokyo   |
|  3 | alice | china   |
+----+-------+---------+
3 rows in set (0.01 sec)


mysql> SELECT id,name FROM employee ORDER BY 1 DESC;
+----+-------+
| id | name  |
+----+-------+
|  3 | alice |
|  2 | bob   |
|  1 | carol |
+----+-------+
3 rows in set (0.00 sec)


mysql> SELECT id,name FROM employee ORDER BY 2;
+----+-------+
| id | name  |
+----+-------+
|  3 | alice |
|  2 | bob   |
|  1 | carol |
+----+-------+
3 rows in set (0.00 sec)

以上。