数据库数据排序完后，只显示相同id的前三条数据

1.以user_q倒序显示前三条记录
$sql='select * from daily_report as main where (
select count(1) FROM daily_report AS sub where  main.server_id = sub.server_id and main.user_q< sub.active_user_q ) < 3  order by user_q DESC;
$Report=$Model->query($sql);

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2.每个mach_id 只显示两条数据
SELECT *
FROM tbl_mt_log a
WHERE   2 > ( SELECT count(*)
               FROM  tbl_mt_log
               WHERE mach_id = a.mach_id
               AND mt > a.mt)
ORDER BY a.mach_id, a.mt DESC