Question

我有这样的查询，

SELECT b.user_id,b.first_name, b.last_name, b.email_id, 
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE a.email_receiver_id = b.user_id 
AND a.email_sender_id= 20  
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id  
UNION  
SELECT b.user_id,b.first_name, b.last_name, b.email_id, 
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE a.email_sender_id = b.user_id  
AND a.email_receiver_id= 20  
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id;

它的输出是 -

user_id  first_name  last_name  email_id                   sharedFiles  
17       Mohan       Sharma     mohan.guptademo@gmail.com  2            
17       Mohan       Sharma     mohan.guptademo@gmail.com  1

它显示两个不同的记录。但我想要这样的输出 -

user_id  first_name  last_name  email_id                   sharedFiles  
17       Mohan       Sharma     mohan.guptademo@gmail.com  3

我是mysql的新手，所以请帮助我如何获得此输出。

谢谢。

Answer 1

将查询用作子查询可以进行其他分组和汇总。请查看以下查询：

SELECT (b.user_id,b.first_name, b.last_name, b.email_id, SUM(b.sharedFiles) 
FROM (
    SELECT b.user_id,b.first_name, b.last_name, b.email_id, COUNT(DISTINCT a.file_id) AS sharedFiles  
    FROM email_history a, users b  
    WHERE a.email_receiver_id = b.user_id 
    AND a.email_sender_id= 20  
    GROUP BY b.user_id,b.first_name, b.last_name, b.email_id  UNION  
    UNION
    SELECT b.user_id,b.first_name, b.last_name, b.email_id, COUNT(DISTINCT a.file_id) AS sharedFiles  
    FROM email_history a, users b  
    WHERE a.email_sender_id = b.user_id  
    AND a.email_receiver_id= 20  
    GROUP BY b.user_id,b.first_name, b.last_name, b.email_id;
) AS b
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id

Answer 2

SELECT b.user_id,b.first_name, b.last_name, b.email_id, SUM(sharedFiles)as sharedFiles
FROM(
SELECT b.user_id,b.first_name, b.last_name, b.email_id, 
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE a.email_receiver_id = b.user_id 
AND a.email_sender_id= 20  
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id  
UNION  
SELECT b.user_id,b.first_name, b.last_name, b.email_id, 
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE a.email_sender_id = b.user_id  
AND a.email_receiver_id= 20  
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id)x
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id;

Answer 3

管理UNION结果的一般解决方案是将其放在子查询中，并在外部函数中进行分组，如下所示：

SELECT t.user_id, t.first_name, t.last_name, t.email_id, SUM(t.sharedFiles)
FROM 
(SELECT b.user_id,b.first_name, b.last_name, b.email_id,
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE a.email_receiver_id = b.user_id 
AND a.email_sender_id= 20    
UNION  
SELECT b.user_id,b.first_name, b.last_name, b.email_id, 
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE a.email_sender_id = b.user_id  
AND a.email_receiver_id=20) t 
GROUP BY t.user_id;

但是，似乎您的精确请求可以通过OR进行单个查询。

SELECT b.user_id,b.first_name, b.last_name, b.email_id, 
COUNT(DISTINCT a.file_id) AS sharedFiles  
FROM email_history a, users b  
WHERE (a.email_receiver_id = b.user_id 
AND a.email_sender_id= 20) OR (a.email_sender_id = b.user_id  
AND a.email_receiver_id= 20) 
GROUP BY b.user_id,b.first_name, b.last_name, b.email_id

如何将这两个结果合并为一个在mysql中？

3 个答案: