mysql 数据库查询

1、根据时间查询所有用户最新一条数据

'select user,password,max(date) as date from user group by user'

注意：此处的‘‘user,password’’不能使用“*”号代替，否则会出错（具体原因不明）

2、查询某一用户最新一条数据

'select * from user where user = " ' + userName + ' " order by date desc limit 1'

注意：此处的“userName”是一个变量，一定得注意sql语句中的双引号

3、返回值经过简单的计算

'select (number*3-2)/2 as number from user where user = " ' + userName + ' " order by date desc limit 1'

4、查询某用户在某一时间段所有数据

'select * from user where user = " ' + userName + ' " and date > " ' + startTime + ' " and date < " ' + endTime + ' " '