PostgreSQL ORDER BY 语句-PostgreSQL入门教程

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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：
```
maxiaokedb# 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：
```
maxiaokedb=# 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：
```
maxiaokedb=# 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：
```
maxiaokedb=# 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)
```

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