SQL join和count do net将它组合在一起

Question

我是SQL的初学者,同时在加入和计数方面遇到了一些麻烦.首先让我解释一下我的两张桌子.我有以下内容:

   Table: AnalysePageview
          id       title     session      more
        -----------------------------------------------------
           1         a           10        0
           2         b           20        1
           3         c           30        1            
           4         d           40        1
           5         e           50        1
           6         f           60        0

    Table: AnalyseEvent
          id       name     session      more
        -----------------------------------------------------
           1         a           10        0
           2         b           10        1
           3         c           10        1            
           4         d           20        1

我想加入这两个并添加这样一行:

    New Table:
          id       name       session   counts (out off AnalyseEvent)
        -----------------------------------------------------
           1         a           10        3
           2         b           20        1
           3         c           30        0            
           4         d           40        0
           5         e           50        0
           6         f           60        0

我刚试过这个:

SELECT *, 
       COUNT( AnalyseEvent.session ) AS totalViews 
FROM AnalysePageview  
LEFT JOIN AnalyseEvent ON AnalysePageview.session = AnalyseEvent.session

谢谢你提前帮助.(我的小初学者解释)

Answer 1

你需要一个group by:

SELECT apv.id, apv.name, apv.session, COUNT( ae.session ) AS totalViews
FROM AnalysePageview  apv LEFT JOIN
     AnalyseEvent ae
     ON apv.session = ae.session
GROUP BY apv.id, apv.name, apv.session;

我还添加了表别名,以使查询更容易编写和读取.