求一个单表的SQL语句

[learnner]

有表4个字段
id(主键) uid mydatetime amount

现在要找出uid=5的mydatetime最大的那条记录，表的记录比较多，求最高效写法。非高效写法也没有写出来

我的尝试：

select id,uid,max(mydatetime),amount from table1 where uid=5 group by id,uid,amount;

结果是多条记录

请帮助

[nicenight]

要只是用一次就不用管高不高效了：

select * from table1 where uid=5 order by mydatetime desc limit 1

[rucypli]

高效的做法就是uid上必须有索引

[徐明勋]

select a.id,a.uid,a.mydatetime,a.amount from test15 a inner join
(select uid,max(mydatetime) tm from test15 where uid=5) b
on a.uid=b.uid and a.mydatetime=b.tm where a.uid=5

[ACMAIN_CHM]

select * 
from table1
where uid=5
order by mydatetime desc 
limit 1;

[ACMAIN_CHM]

如果为了提高效率，则需要创建 （uid，mydatetime）的索引。