#通过四则运算查询
SELECT name, salary*12 FROM employee;
SELECT name, salary*12 AS Annual_salary FROM employee;
SELECT name, salary*12 Annual_salary FROM employee;
查看年薪
salary*12
mysql> select name,salary*12 from employee;
+------------+-------------+
| name | salary*12 |
+------------+-------------+
| alex | 12000003.72 |
| yuanhao | 42000.00 |
| liwenzhou | 25200.00 |
| jingliyang | 108000.00 |
| jinxin | 360000.00 |
| 成龙 | 120000.00 |
| 歪歪 | 36001.56 |
| 丫丫 | 24004.20 |
| 丁丁 | 12004.44 |
| 星星 | 36003.48 |
| 格格 | 48003.96 |
| 张野 | 120001.56 |
| 程咬金 | 240000.00 |
| 程咬银 | 228000.00 |
| 程咬铜 | 216000.00 |
| 程咬铁 | 204000.00 |
+------------+-------------+
16 rows in set (0.10 sec)
查出来的结果 这是一张虚拟表
因为查出来结果 标注红色的 salary*12 不太直观 利用另外一种方式查表
as 给字段起别名
select 字段 as 别名 from 表名
mysql> select name,salary*12 as Annual_salary from employee;
+------------+---------------+
| name | Annual_salary |
+------------+---------------+
| alex | 12000003.72 |
| yuanhao | 42000.00 |
| liwenzhou | 25200.00 |
| jingliyang | 108000.00 |
| jinxin | 360000.00 |
| 成龙 | 120000.00 |
| 歪歪 | 36001.56 |
| 丫丫 | 24004.20 |
| 丁丁 | 12004.44 |
| 星星 | 36003.48 |
| 格格 | 48003.96 |
| 张野 | 120001.56 |
| 程咬金 | 240000.00 |
| 程咬银 | 228000.00 |
| 程咬铜 | 216000.00 |
| 程咬铁 | 204000.00 |
+------------+---------------+
16 rows in set (0.10 sec)
不加as也可以 默认后面就是别名
mysql> select name,salary*12 Annual_salary from employee;
+------------+---------------+
| name | Annual_salary |
+------------+---------------+
| alex | 12000003.72 |
| yuanhao | 42000.00 |
| liwenzhou | 25200.00 |
| jingliyang | 108000.00 |
| jinxin | 360000.00 |
| 成龙 | 120000.00 |
| 歪歪 | 36001.56 |
| 丫丫 | 24004.20 |
| 丁丁 | 12004.44 |
| 星星 | 36003.48 |
| 格格 | 48003.96 |
| 张野 | 120001.56 |
| 程咬金 | 240000.00 |
| 程咬银 | 228000.00 |
| 程咬铜 | 216000.00 |
| 程咬铁 | 204000.00 |
+------------+---------------+
16 rows in set (0.00 sec)