分组取前n条

select * from record_base_log r,(SELECT max(id) as id from record_base_log
GROUP BY udid) t
where r.id=t.id


SELECT a.*, count(a.id) from record_base_log a
inner join record_base_log b
on a.udid=b.udid and a.id <= b.id
GROUP BY  a.udid, b.id
HAVING COUNT(a.id) <= 1