mysql 数据操作 单表查询 concat()函数 定义显示格式

#定义显示格式

concat() 函数用于连接字符串

类似于python 格式化操作
print("姓名:%s" % name)
或者 用,拼接一个一个的变量
print("alex","mike","jack")

>>> print("alex","mike","jack")
alex mike jack

mysql> select concat('姓名:',name) from employee;
+------------------------+
| concat('姓名:',name)   |
+------------------------+
| 姓名:alex              |
| 姓名:yuanhao           |
| 姓名:liwenzhou         |
| 姓名:jingliyang        |
| 姓名:jinxin            |
| 姓名:成龙              |
| 姓名:歪歪              |
| 姓名:丫丫              |
| 姓名:丁丁              |
| 姓名:星星              |
| 姓名:格格              |
| 姓名:张野              |
| 姓名:程咬金            |
| 姓名:程咬银            |
| 姓名:程咬铜            |
| 姓名:程咬铁            |
+------------------------+
16 rows in set (0.00 sec)

加上性别 别名

mysql> select concat('姓名:',name,'性别:',sex) as info from employee;
+--------------------------------+
| info                           |
+--------------------------------+
| 姓名:alex性别:male             |
| 姓名:yuanhao性别:male          |
| 姓名:liwenzhou性别:male        |
| 姓名:jingliyang性别:female     |
| 姓名:jinxin性别:male           |
| 姓名:成龙性别:male             |
| 姓名:歪歪性别:female           |
| 姓名:丫丫性别:female           |
| 姓名:丁丁性别:female           |
| 姓名:星星性别:female           |
| 姓名:格格性别:female           |
| 姓名:张野性别:male             |
| 姓名:程咬金性别:male           |
| 姓名:程咬银性别:female         |
| 姓名:程咬铜性别:male           |
| 姓名:程咬铁性别:female         |
+--------------------------------+
16 rows in set (0.00 sec)

在别名后面 加上薪资

mysql> select concat('姓名:',name,'性别:',sex) as info,salary from employee;
+--------------------------------+------------+
| info                           | salary     |
+--------------------------------+------------+
| 姓名:alex性别:male             | 1000000.31 |
| 姓名:yuanhao性别:male          |    3500.00 |
| 姓名:liwenzhou性别:male        |    2100.00 |
| 姓名:jingliyang性别:female     |    9000.00 |
| 姓名:jinxin性别:male           |   30000.00 |
| 姓名:成龙性别:male             |   10000.00 |
| 姓名:歪歪性别:female           |    3000.13 |
| 姓名:丫丫性别:female           |    2000.35 |
| 姓名:丁丁性别:female           |    1000.37 |
| 姓名:星星性别:female           |    3000.29 |
| 姓名:格格性别:female           |    4000.33 |
| 姓名:张野性别:male             |   10000.13 |
| 姓名:程咬金性别:male           |   20000.00 |
| 姓名:程咬银性别:female         |   19000.00 |
| 姓名:程咬铜性别:male           |   18000.00 |
| 姓名:程咬铁性别:female         |   17000.00 |
+--------------------------------+------------+
16 rows in set (0.00 sec)

用concat() 拼接 
查询年薪

mysql> select concat('姓名:',name,'性别:',sex) as info ,concat('年薪:',salary*12) as Annual_salary from employee;
+--------------------------------+--------------------+
| info                           | Annual_salary      |
+--------------------------------+--------------------+
| 姓名:alex性别:male             | 年薪:12000003.72   |
| 姓名:yuanhao性别:male          | 年薪:42000.00      |
| 姓名:liwenzhou性别:male        | 年薪:25200.00      |
| 姓名:jingliyang性别:female     | 年薪:108000.00     |
| 姓名:jinxin性别:male           | 年薪:360000.00     |
| 姓名:成龙性别:male             | 年薪:120000.00     |
| 姓名:歪歪性别:female           | 年薪:36001.56      |
| 姓名:丫丫性别:female           | 年薪:24004.20      |
| 姓名:丁丁性别:female           | 年薪:12004.44      |
| 姓名:星星性别:female           | 年薪:36003.48      |
| 姓名:格格性别:female           | 年薪:48003.96      |
| 姓名:张野性别:male             | 年薪:120001.56     |
| 姓名:程咬金性别:male           | 年薪:240000.00     |
| 姓名:程咬银性别:female         | 年薪:228000.00     |
| 姓名:程咬铜性别:male           | 年薪:216000.00     |
| 姓名:程咬铁性别:female         | 年薪:204000.00     |
+--------------------------------+--------------------+
16 rows in set (0.00 sec)