按name分组取val最大的值所在行的数据
select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name
select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val) （不建议）
select a.* from tb a,(select name,max(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
select a.* from tb a inner join (select name , max(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name （不建议）
select * from (select * from tb ORDER BY val desc) temp GROUP BY name ORDER BY val desc;
https://www.cnblogs.com/fps2tao/p/9041175.html
