MySQL中order by的学习使用

order by用于对查询出来的数据进行排序操作，用两个例子可以很容易理解这个参数。

1，普通查询。

mysql> select * from groups;
+----+---------------------+---------------------+---------------------+----------+------------+
| id | created_at          | updated_at          | deleted_at          | group_id | group_name |
+----+---------------------+---------------------+---------------------+----------+------------+
|  1 | NULL                | 2020-06-16 22:07:02 | 2020-06-16 22:14:40 |        1 | 开发组     |
|  2 | 2020-06-15 23:37:25 | 2020-06-15 23:37:25 | NULL                |        2 | 测试组     |
|  3 | 2020-06-16 22:17:07 | 2020-06-16 22:17:07 | NULL                |        3 | 运营组     |
|  4 | 2020-06-16 22:17:15 | 2020-06-16 22:17:15 | NULL                |        4 | 客服组     |
|  5 | 2020-06-16 22:17:26 | 2020-06-16 22:17:26 | NULL                |        5 | OPS        |
+----+---------------------+---------------------+---------------------+----------+------------+
5 rows in set (0.00 sec)

默认情况下，查出来的数据是按照主键ID正序排列的。

2，基于ID进行排序。

mysql> select * from groups order by id desc;
+----+---------------------+---------------------+---------------------+----------+------------+
| id | created_at          | updated_at          | deleted_at          | group_id | group_name |
+----+---------------------+---------------------+---------------------+----------+------------+
|  5 | 2020-06-16 22:17:26 | 2020-06-16 22:17:26 | NULL                |        5 | OPS        |
|  4 | 2020-06-16 22:17:15 | 2020-06-16 22:17:15 | NULL                |        4 | 客服组     |
|  3 | 2020-06-16 22:17:07 | 2020-06-16 22:17:07 | NULL                |        3 | 运营组     |
|  2 | 2020-06-15 23:37:25 | 2020-06-15 23:37:25 | NULL                |        2 | 测试组     |
|  1 | NULL                | 2020-06-16 22:07:02 | 2020-06-16 22:14:40 |        1 | 开发组     |
+----+---------------------+---------------------+---------------------+----------+------------+
5 rows in set (0.00 sec)

注意其中的 desc表示用倒序排列。

如果想要正序排列，则使用asc:

mysql> select * from groups order by id asc;
+----+---------------------+---------------------+---------------------+----------+------------+
| id | created_at          | updated_at          | deleted_at          | group_id | group_name |
+----+---------------------+---------------------+---------------------+----------+------------+
|  1 | NULL                | 2020-06-16 22:07:02 | 2020-06-16 22:14:40 |        1 | 开发组     |
|  2 | 2020-06-15 23:37:25 | 2020-06-15 23:37:25 | NULL                |        2 | 测试组     |
|  3 | 2020-06-16 22:17:07 | 2020-06-16 22:17:07 | NULL                |        3 | 运营组     |
|  4 | 2020-06-16 22:17:15 | 2020-06-16 22:17:15 | NULL                |        4 | 客服组     |
|  5 | 2020-06-16 22:17:26 | 2020-06-16 22:17:26 | NULL                |        5 | OPS        |
+----+---------------------+---------------------+---------------------+----------+------------+
5 rows in set (0.00 sec)

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