取出某一列相同,而另一列最大的记录

create table tb(col1 varchar(10),col2 int,col3 int,col4 int,col5 varchar(10),col6 varchar(10))
insert into tb select 'Y',10,5,123,'A','你好'
insert into tb select 'C',15,6,231,'A','你好啊'
insert into tb select 'C',15,5,321,'A','你好吗'
insert into tb select 'F',20,8,111,'A','你真的好'

select * from tb t where not exists(
select 1 from tb where col1=t.col1 and col3>t.col3
)