1. 分组取最大数据那个值

SELECT a.user_id,b.id,b.score
FROM users a,socre b
where score= (select max(score) from socre where user_id = a.user_id ) 
group by user_id;

2.普通的取最大的那个值

-- order by 字段名 desc limit 1
select  a.user_id from users a order by a.user_id desc limit 1;
-- 使用max函数
select max(id) from users