在本教程中，我们将学习为MySQL中的列和表创建和使用别名。

我们使用别名为列和表重新命名。
别名将保留到查询执行为止。
这有助于我们根据需要创建更有意义的列和表名。

对于本教程，我们将使用在CREATE Table教程中创建的employee表。

员工表

mysql> SELECT * FROM employee;
+------------+-----------+----------+----------------------+-------+------------+---------------------+---------------------+
| employeeid | firstname | lastname | email                | score | birthday   | lastmodified        | created             |
+------------+-----------+----------+----------------------+-------+------------+---------------------+---------------------+
| e01        |      |   | @example.com    |     7 | 1900-01-01 | 2016-02-04 06:08:10 | 2016-01-01 01:01:01 |
| e02        | John      | Doe      | [email protected]  |     7 | 1900-02-03 | 2016-02-04 06:08:10 | 2016-01-01 01:01:04 |
| e03        | Jane      | Doe      | [email protected]  |     7 | 1900-05-20 | 2016-02-04 06:08:10 | 2016-01-01 01:01:04 |
| e04        | Tin       | Tin      | [email protected]   |     7 | 1900-10-20 | 2016-02-04 06:08:10 | 2016-01-01 01:02:03 |
| e05        | Bob       | Coder    | [email protected] |     7 | 1900-08-20 | 2016-02-04 06:08:10 | 2016-01-01 01:02:10 |
+------------+-----------+----------+----------------------+-------+------------+---------------------+---------------------+
5 rows in set (0.00 sec)

列的别名语法

SELECT column_name AS alias_name
FROM table_name;

表的别名语法

SELECT tbl.column_name
FROM table_name tbl;

栏别名

在以下示例中，我们将为" employee"表的" employeeid"列创建别名" id"。

mysql> SELECT employeeid AS id, firstname, lastname, email FROM employee;
+-----+-----------+----------+----------------------+
| id  | firstname | lastname | email                |
+-----+-----------+----------+----------------------+
| e01 |      |   | @example.com    |
| e02 | John      | Doe      | [email protected]  |
| e03 | Jane      | Doe      | [email protected]  |
| e04 | Tin       | Tin      | [email protected]   |
| e05 | Bob       | Coder    | [email protected] |
+-----+-----------+----------+----------------------+
5 rows in set (0.00 sec)

表别名

在下面的示例中，我们将为" employee"表创建别名" e"。

mysql> SELECT e.employeeid, e.firstname, e.lastname FROM employee e;
+------------+-----------+----------+
| employeeid | firstname | lastname |
+------------+-----------+----------+
| e01        |      |   |
| e02        | John      | Doe      |
| e03        | Jane      | Doe      |
| e04        | Tin       | Tin      |
| e05        | Bob       | Coder    |
+------------+-----------+----------+
5 rows in set (0.01 sec)