题目：有个xiaofei表里面的字段如果。
要求用一条sql语句查询出所有user的最后一次的消费记录

呃 看来沉的好快~1

如果主键是 按时间循序添加的话
select max 后 group by userid
再与本表相连？
几年没开发了，脑子都不好用了

确实应该这样

mysql：先让它执行order by的语句
SELECT userid,money,xiaofeidate FROM (SELECT * FROM xiaofei ORDER BY xiaofeidate DESC) c
GROUP BY userid ORDER BY xiaofeidate DESC
Oracle：
select userid,money,xiaofeidate
from (select userid,money,xiaofeidate,row_number()over
(partition by userid order by xiaofeidate desc) c
from xiaofei) a where a.c=1 order by xiaofeidate desc
mysql&Oracle： 通过同时匹配2个字段来查询
select * from xiaofei a where exists( select 1 from (
select userid,max(xiaofeidate) xiaofeidate from xiaofei
group by userid) b where a.userid=b.userid and a.xiaofeidate=b.xiaofeidate)

select * from xiaofei where xiaofeidate in (SELECT max(xiaofeidate) FROM xiaofei group by userid)

目测5楼的方法最好
9楼的跟我3楼说的类似

菜鸟问a,not exists()哪来的，什么意思，谢谢

in 和 not in 意思差不多
你可以百度下这个的用法和区别

效率比 in 之类的高

不就是要查出第一条记录么？
select xf.* from xiaofei xf where to_char(xf.xiaofeidate)=(select to_char(max(x.xiaofeidate)) from xiaofei x)

最厚一条记录？？用@@identity吧，详情请按F1

你自己想下
select to_char(max(x.xiaofeidate)) from xiaofei x) 你这里是获得所有记录的最大的日期，而是每个用户的最大日期~！ 看懂题目再做

select main(里面是要求出的数据) from 表名

挺简单的：
Select userid, money, xiaofeidate
From xiaofei x
Where xiaofeidate in (Select MAX(xiaofeidate) From xiaofei
Where userid = x.userid)