Question

我想要计算许多喜欢我在我的数据库中的特定帖子我创建了这个简单的查询显示有多少像我有一个资源“帖子”但是当我添加到主脚本时它会错过它

SELECT     COUNT(Likes.resourceID) AS Count_resID, Resources.Id
FROM         Likes INNER JOIN
                      Resources ON Likes.resourceID = Resources.Id
GROUP BY Resources.Id

Result 
Count_resID Id
----------- -----------
1           53
2           54
2           60
2           61
1           62

(5 row(s) affected)
SELECT     a.Id, a.summary, a.pageId, a.name, a.createdOn, COUNT(Likes.resourceID) AS Count_resID
FROM         Resources AS a INNER JOIN
                      Topics_Resources AS b ON a.Id = b.ResourceID INNER JOIN
                      Skills_Resources AS c ON a.Id = c.ResourceID INNER JOIN
                      Types AS d ON a.typeId = d.Id INNER JOIN
                      Modules AS m ON a.ModuleId = m.ModuleID INNER JOIN
                      ContentItems AS ci ON m.ModuleID = ci.ModuleID INNER JOIN
                      Tabs AS t ON t.TabID = ci.TabID INNER JOIN
                      TabModules AS tb ON t.TabID = tb.TabID INNER JOIN
                      Likes ON a.Id = Likes.resourceID LEFT OUTER JOIN
                      HtmlText AS h ON tb.ModuleID = h.ModuleID
GROUP BY a.Id, a.summary, a.pageId, a.name, a.createdOn 
Id          summary                             pageId                                                            name           createdOn                 Count_resID
----------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------
53          jihuih                               http://localhost/ideapark/testpage99.aspx                        jklhjk         2013-05-10 07:24:21.833    12
54          1                                    http://localhost/ideapark/testpage33.aspx                        sdvs           2013-05-09 07:24:21.833    2
60          sdvsdv                               http://localhost/ideapark/tesCreatedate.aspx                     dsvsdv         2013-05-13 07:32:13.133    8
61          newtest                              http://localhost/ideapark/newtest.aspx                           newTest       2013-05-13 10:35:08.027     2
62          sdvsdvds                             http://localhost/ideapark/page21.aspx                            svdsvs        2013-05-14 14:06:15.603     35

(5 row(s) affected)

Answer 1

根据您的结果更改，您使用加入表格的标准之一存在问题。您必须确保连接中的表与基表具有一对一的比率。

Answer 2

问题是您正在连接多个表，并且这些表中的多个表具有1-n关系。您正在获得笛卡尔产品，而您并不期望它。

解决此问题的正确方法是在加入之前进行子查询汇总。

但是，您可以使用count(distinct)进行快速简便的修复。请改用此select语句：

SELECT     a.Id, a.summary, a.pageId, a.name, a.createdOn,
           COUNT(distinct Likes.Id) AS Count_resID;

这假设likes中的每条记录都有id来唯一标识它。

更好的解决方法（特别是如果重新使用此查询）涉及更改from联接：

                  TabModules AS tb ON t.TabID = tb.TabID INNER JOIN
                  Likes ON a.Id = Likes.resourceID LEFT OUTER JOIN

类似于：

                  . . .
                  TabModules AS tb ON t.TabID = tb.TabID INNER JOIN
                  (select l.resourceId, count(*) as NumLikes
                   from Likes l
                  ) l ON a.Id = l.resourceID LEFT OUTER JOIN
                  . . .

然后在NumLikes子句中引用select。

怎么算数

2 个答案: