《Mysql必讀MySQL獲取所有分類的前N條記錄》要點：
本文介紹了Mysql必讀MySQL獲取所有分類的前N條記錄，希望對您有用。如果有疑問，可以聯(lián)系我們。
MYSQL必讀比如有文章表 Article(Id,Category,InsertDate),現(xiàn)在要用SQL找出每種類型中時間最新的前N個數(shù)據(jù)組成的集合,一段不錯的代碼,留存?zhèn)溆?br>
MYSQL必讀
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
MYSQL必讀@N 就是你要取多少條
MYSQL必讀下面是我用到了一個產(chǎn)品分類表中,superId是大分類,prcid是產(chǎn)品分類.能用SQL完成的功能就要盡量用SQL語句來完成,這既簡潔又高效.
MYSQL必讀
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
MYSQL必讀需求是這樣的(CSDN上的一個問題)：mysql中有個表：article(字段：id,type,date),type有1-10,10種類型.現(xiàn)在要用SQL找出每種類型中時間最新的前N個數(shù)據(jù)組成的集合.
MYSQL必讀這個問題應(yīng)該有很多方法可以實現(xiàn),下面就來說說在網(wǎng)上看到的一位高手的實現(xiàn)(用一條SQL語句實現(xiàn)的,個人感覺非常好,所以拿來和大家分享)：?
MYSQL必讀
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
MYSQL必讀注：上面sql語句中的2代表的就是前面提到的N.
MYSQL必讀以上所述就是本文的全部內(nèi)容了,希望大家能夠喜歡.
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