SQL 基础教程

SQL 基础命令

SQL 高级教程

SQL Alias (别名)

通过使用 SQL，可以为列名称和表名称指定别名（Alias）。

表的 SQL Alias 语法

SELECT column_name(s)
FROM table_name
AS alias_name

列的 SQL Alias 语法

SELECT column_name AS alias_name
FROM table_name

Alias 实例: 使用表名称别名

假设我们有两个表分别是："Person" 和 "Product_Order"。我们分别为它们指定别名 "p" 和 "po"。

现在，我们希望列出 "John Adams" 的所有定单。

mysql> select * from product_order;
+----------+-----------+---------+---------+
| LastName | FirstName | Product | orderID |
+----------+-----------+---------+---------+
| Adams    | John      | tree    |       2 |
| Gates    | Bill      | pot     |       5 |
+----------+-----------+---------+---------+
2 rows in set (0.00 sec)

mysql> select * from persons;
+----------+----------+-----------+----------------+----------+
| PersonID | LastName | FirstName | Address        | City     |
+----------+----------+-----------+----------------+----------+
|        1 | Adams    | John      | Oxford Street  | London   |
|        2 | Bush     | George    | Fifth Avenue   | New York |
|        3 | Carter   | Thomas    | Changan Street | Beijing  |
|        4 | Gates    | Bill      | Xuanwumen 10   | Beijing  |
+----------+----------+-----------+----------------+----------+
4 rows in set (0.00 sec)

mysql> select po.OrderID, p.LastName, p.FirstName from persons AS p, product_order AS po where p.LastName='Adams' and p.FirstName='John';
+---------+----------+-----------+
| OrderID | LastName | FirstName |
+---------+----------+-----------+
|       2 | Adams    | John      |
|       5 | Adams    | John      |
+---------+----------+-----------+
2 rows in set (0.01 sec)

别名使查询程序更易阅读和书写。

Alias 实例: 使用一个列名别名

mysql> select LastName AS Family, FirstName AS Name from persons;
+--------+--------+
| Family | Name   |
+--------+--------+
| Adams  | John   |
| Bush   | George |
| Carter | Thomas |
| Gates  | Bill   |
+--------+--------+