SQL 别名的使用

SQL中别名可以分为表别名和列别名

列的 SQL 别名语法

SELECT column_name AS alias_name FROM table_name;

表的 SQL 别名语法

SELECT column_name(s) FROM table_name AS alias_name;

实例数据

+----+---------------+---------------------------+-------+---------+
| id | name          | url                       | alexa | country |
+----+---------------+---------------------------+-------+---------+
|  1 | 百度        | https://www.baidu.com/    |     1 | CN     |
|  2 | 淘宝          | https://www.taobao.com/   |    13 | CN      |
|  5 | Facebook      | https://www.facebook.com/ |     3 | USA     |
|  7 | stackoverflow | http://stackoverflow.com/ |     0 | IND     |
+----+---------------+---------------------------+-------+---------+

列别名

SQL 语句指定了两个别名，一个是 name 列的别名，一个是 country 列的别名。

注意：如果列名称包含空格，要求使用双引号或方括号：

SELECT name AS n, country AS c FROM website;

+----+---------+
| n      | c |
+----+-----+
| 百度     | CN     |
| 淘宝      | CN      |
| Facebook   | USA     |
| stackoverflow  | IND     |
+----+-----+

三个列（url、alexa 和 country）结合在一起，并创建一个名为 "base_info" 的别名：

SELECT name, CONCAT(url, ', ', alexa, ', ', country) AS base_info FROM website;

+----+--------------------------------------------------------+
| name          |base_info                                    |
+----+----------------------------------------------------------+
| 百度        | https://www.baidu.com/ , 1,CN                  |
| 淘宝          | https://www.taobao.com/, 13 , CN             |
| Facebook      | https://www.facebook.com/,3, USA            |
| stackoverflow | http://stackoverflow.com/,0 ,IND           |
+----+--------------------------------------------------------+

表别名

SELECT w.name, w.url,w.alexa,w.country
FROM website AS w WHERE w.name="百度";

+----+---------------+---------------------------+-------+---------+
| name          | url                       | alexa | country |
+----+---------------+---------------------------+-------+---------+
| 百度        | https://www.baidu.com/    |     1 | CN     |
+----+---------------+---------------------------+-------+---------+