本文介绍了在sql查询中添加第三个查询的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我使用以下查询从两个表中获取记录。现在我想以这样的方式编辑我的查询,它也从第三个表中获取记录。我的第三个查询将类似于table3中的select count(*),其中user_id = user_id。
我不擅长使用连接。这就是我问这个问题的原因。
i am using the below query to fetch record from two tables. Now i want to edit my query in such a way that it fetch record also from third table. my third query will be like select count(*) from table3 where user_id=user_id.
I am not good in using joins. That's why i am asking this question.
SELECT table1.displayname,table2.title
FROM table1
INNER JOIN table2 ON talbe2.user_id = table1.userid
任何帮助都将不胜感激。
Any help would be appreciated.
推荐答案
SELECT table1.displayname,table2.title ,count(table3.user_id)
FROM table1
INNER JOIN table2 ON table2.user_id = table1.userid inner join table2 on table3.user_id = table1.userid group by table1.displayname,table2.title
使用聚合函数时需要分组依据
you need Group by clause when you use aggregate function
SELECT
T1.displayname
,T2.title
,COUNT(T3.user_id) AS No_of_records_in_Table3
FROM Table1 T1
INNER JOIN Table2 T2
ON T2.user_id = T1.userid
INNER JOIN Table3 T3
ON T3.user_id = T1.userid
GROUP BY T1.displayname, T2.title
您还应该阅读。
SELECT table1.displayname,table2.title, (SELECT COUNT(*) FROM Table3 WHERE table1.userid = Table3.userid) AS CountOfSomething
FROM table1
INNER JOIN table2 ON talbe2.user_id = table1.userid
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