MySQL获取所有分类的前N条记录

SELECT A1.* 
FROM Article AS A1 
   INNER JOIN (SELECT A.Category,A.InsertDate 
         FROM Article AS A 
           LEFT JOIN Article AS B 
            ON A.Category = B.Category 
              AND A.InsertDate <= B.InsertDate 
         GROUP BY A.Category,A.InsertDate 
         HAVING COUNT(B.InsertDate) <= @N 
  ) AS B1 
  ON A1.Category = B1.Category 
    AND A1.InsertDate = B1.InsertDate 
ORDER BY A1.Category,A1.InsertDate DESC

SELECT
  A1.*
FROM
  prcKx AS A1
INNER JOIN (
  SELECT
    A.superId,
    A.prcid
  FROM
    prcKx AS A
  LEFT JOIN prcKx AS B ON A.superId = B.superId
  AND A.prcid <= B.prcid
  GROUP BY
    A.superId,
    A.prcid
  HAVING
    COUNT(B.prcid) <= 7
) AS B1 ON A1.superId = B1.superId
AND A1.prcid = B1.prcid
ORDER BY
  superId,
  prcid

select a1.* from article a1
inner join
(select a.type,a.date from article a left join article b
on a.type=b.type and a.date<=b.date 
group by a.type,a.date
having count(b.date)<=2
)b1
on a1.type=b1.type and a1.date=b1.date
order by a1.type,a1.date desc