如何使用连接编写此查询？

Question

我有一个表活动，其中包含发送活动邮件的详细信息。

campaign_table: campaign_id campaign_name flag 
         1   test1  1 
         2   test2  1 
         3   test3  0 

另一个表具有活动活动细节的活动活动。

campaign_activity: campaign_id is_clicked is_opened 
          1    0   1   
          1    1   0   
          2    0   1 
          2    1   0 

我想用标志值3和值为1和列数is_clicked列与is_opened值1在一个查询数所有广告活动。

ie. campaign_id campaign_name numberofclicks numberofopens 
      1   test1   1    1 
      2   test2   1    1 

我这样做是使用子查询与查询：

select c.campaign_id,c.campaign_name, 
(SELECT count(campaign_id) from campaign_activity WHERE campaign_id=c.id AND is_clicked=1) as numberofclicks, 
(SELECT count(campaign_id) from campaign_activity WHERE campaign_id=c.id AND is_clicked=1) as numberofopens 
FROM 
campaign c 
WHERE c.flag=1 

但人们说，使用子查询是不是一个很好的编码习惯，你必须使用联接，而不是子查询。但我不知道如何使用连接获得相同的结果。我咨询了一些同事，他们说在这种情况下不可能加入。使用连接可以得到相同的结果吗？如果是，请告诉我如何。

Answer 1

这应该可以做到。如果您想要包含没有任何活动的广告系列，请将INNER JOIN替换为LEFT OUTER JOIN。

SELECT 
    c.Campaign_ID 
    , c.Campaign_Name 
    , SUM(CASE WHEN a.Is_Clicked = 1 THEN 1 ELSE 0 END) AS NumberOfClicks 
    , SUM(CASE WHEN a.Is_Opened = 1 THEN 1 ELSE 0 END) AS NumberOfOpens 
FROM 
    dbo.Campaign c 
INNER JOIN 
    dbo.Campaign_Activity a 
ON a.Campaign_ID = c.Campaign_ID 
GROUP BY 
    c.Campaign_ID 
    , c.Campaign_Name 

Answer 2

我想这应该这样做：

select * from campaign_table inner join campaign_activity on campaign_table.id = campaign_activity.id where campaign_table.flag = 3 and campaign_activity.is_clicked = 1 and campaign_activity.is_opened = 1 

经办人：这是不带电情况下

Answer 3

嗯测试。你想这么简单吗？我不知道我读题吧......

SELECT 
    campaign_table.campaign_id, SUM(is_clicked), SUM(is_opened) 
FROM 
    campaign_table 
    INNER JOIN campaign_activity ON campaign_table.campaign_id = campaign_activity.campaign_id 
WHERE 
    campaign_table.flag = 1 
GROUP BY 
    campaign_table.campaign_id 

注意与INNER JOIN在这里，你将不会看到广告，其中有一个在campaign_activity表中对应的什么都没有。在这种情况下，应该使用LEFT JOIN，并在SUM中将NULL转换为0。 SUM（IFNULL（is_clicked，0））。

Answer 4

假设is_clicked和is_opened是永远只1或0，这应该工作：

select c.campaign_id, c.campaign_name, sum(d.is_clicked), sum(d.is_opened) 
from campaign c inner join campaign_activity d 
on c.campaign_id = d.campaign_id 
where c.flag = 1 
group by c.campaign_id, c.campaign_name 

无子查询。

Answer 5

在它最简单的形式和最强大的形式SQL是这样的：（格式化的可读性）

SELECT 
campaign_table.campaign_ID, campaign_table.campaign_name, Sum(campaign_activity.is_clicked) AS numberofclicks, Sum(campaign_activity.is_open) AS numberofopens 

FROM 
campaign_table INNER JOIN campaign_activity ON campaign_table.campaign_ID = campaign_activity.campaign_ID 

GROUP BY 
campaign_table.campaign_ID, campaign_table.campaign_name, campaign_table.flag 

HAVING 
campaign_table.flag=1;