Question

我得出以下结果:我从三个表格的合并中获得:

SELECT X.*, Y.Name FROM `A` AS X
INNER JOIN `B` AS Y
INNER JOIN `C` AS Z
ON X.id=Y.id AND X.categoryID=Z.categoryID
WHERE X.userID_FK=%d AND X.listID_FK=%d 
ORDER BY Z.categoryRank ASC

页: 1

-------------------------------
  id_FK    userID_FK    vote
-------------------------------

www.un.org/Depts/DGACM/index_french.htm

第1次查询所交回的每个<代码>X.id可在<代码>D表中有多个条目。通常情况下,每名回归者,为了按<代码>id获得表决票, 我这样说:

SELECT SUM(vote) FROM D WHERE `id`=%d

我很想知道,如果现行办法在<条码>O(n)执行时间上产生结果,我是否可以将这两个问题优化为一个单一问题。 <代码>n,是第一个查询点退还的结果数目。

Answer 1

You can simply do it like this

SELECT
X.*,
Y.Name,
(SELECT
   SUM(vote)
   FROM D
   WHERE `id` = X.id) as Count
FROM `A` AS X
INNER JOIN `B` AS Y
INNER JOIN `C` AS Z
ON X.id = Y.id
  AND X.categoryID = Z.categoryID
WHERE X.userID_FK =  % d
AND X.listID_FK =  % d
ORDER BY Z.categoryRank ASC

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