mysql-算术表达式、函数

 

支持 算术表达式

加减乘除

查出年龄列 并且每个加10：

select age + 10 as age from `user`

 

函数

合并字符

select CONCAT(name, '最帅') as name from `user`

 

从左开始截取 字符

//LEFT(name,3) 从左开始截取3个字符
SELECT LEFT(name, 3) as name from `user`

 

从右开始截取 字符

SELECT RIGHT(name, 3) as name from `user`

 

任意位置开始

SELECT SUBSTRING(name, 1, 3) as name from `user`

 

SELECT RAND() as rand FROM `user`  -- 随机数


SELECT SUM(age) as age from `user`  -- 求总和


SELECT AVG(age) as age from `user`  -- 求平均数


SELECT MAX(age) as age from `user`  -- 求最大值


SELECT MIN(age) as age from `user`  -- 求最小值


SELECT COUNT(*) as age from `user`  -- 求个数


SELECT NOW() as now  -- 当前时间


SELECT DATE_ADD(NOW(), INTERVAL 1 DAY) as now  -- 加一天时间

 
SELECT DATE_SUB(NOW(), INTERVAL 1 DAY) as now  -- 减一天时间


select IF(sex = 1, '男', '女') from `user`  --  条件判断