在 PostgreSQL 中，ORDER BY 用于对一列或者多列数据进行升序（ASC）或者降序（DESC）排列。
语法ORDER BY 子句的基础语法如下：
SELECT column-list
FROM table_name
[WHERE condition]
[ORDER BY column1, column2, .. columnN] [ASC | DESC];
您可以在 ORDER BY 中使用一列或者多列，但是必须保证要排序的列必须存在。
ASC 表示升序，DESC 表示降序。
实例创建 COMPANY 表（下载 COMPANY SQL 文件 ），数据内容如下：
runoobdb# select * from COMPANY;
id | name | age | address | salary
----+-------+-----+-----------+--------
1 | Paul | 32 | California| 20000
2 | Allen | 25 | Texas | 15000
3 | Teddy | 23 | Norway | 20000
4 | Mark | 25 | Rich-Mond | 65000
5 | David | 27 | Texas | 85000
6 | Kim | 22 | South-Hall| 45000
7 | James | 24 | Houston | 10000
(7 rows)
下面实例将对结果根据 AGE 字段值进行升序排列：
runoobdb=# SELECT * FROM COMPANY ORDER BY AGE ASC;
得到以下结果：
id | name | age | address | salary
----+-------+-----+----------------------------------------------------+--------
6 | Kim | 22 | South-Hall | 45000
3 | Teddy | 23 | Norway | 20000
7 | James | 24 | Houston | 10000
4 | Mark | 25 | Rich-Mond | 65000
2 | Allen | 25 | Texas | 15000
5 | David | 27 | Texas | 85000
1 | Paul | 32 | California | 20000
(7 rows)
下面实例将对结果根据 NAME 字段值和 SALARY 字段值进行升序排序：
runoobdb=# SELECT * FROM COMPANY ORDER BY NAME, SALARY ASC;
得到以下结果：
id | name | age | address | salary
----+-------+-----+----------------------------------------------------+--------
2 | Allen | 25 | Texas | 15000
5 | David | 27 | Texas | 85000
7 | James | 24 | Houston | 10000
6 | Kim | 22 | South-Hall | 45000
4 | Mark | 25 | Rich-Mond | 65000
1 | Paul | 32 | California | 20000
3 | Teddy | 23 | Norway | 20000
(7 rows)
下面实例将对结果根据NAME字段值进行降序排列：
runoobdb=# SELECT * FROM COMPANY ORDER BY NAME DESC;
得到以下结果：
id | name | age | address | salary
----+-------+-----+----------------------------------------------------+--------
3 | Teddy | 23 | Norway | 20000
1 | Paul | 32 | California | 20000
4 | Mark | 25 | Rich-Mond | 65000
6 | Kim | 22 | South-Hall | 45000
7 | James | 24 | Houston | 10000
5 | David | 27 | Texas | 85000
2 | Allen | 25 | Texas | 15000
(7 rows)
