如何获取SQL中两个表中不匹配的行？

Question

对不起，我写了这个问题更清楚在这里： How to get the nonmatching rows in 2 tables in SQL?

感谢

Answer 1

一种选择使用CHANNELS和SUBSCRIBERS表之间的LEFT JOIN：

SELECT c.ChanID, c.name 
FROM CHANNELS c 
LEFT JOIN SUBSCRIBERS s 
    ON c.ChanID = s.ChanID 
WHERE s.ChanID IS NULL AND 
     c.nickname = 'Jonny' AND  -- not sure about this condition 
     s.nickname = 'Jonny'   -- or this one 

这里是一个视觉什么中间表看起来像合并期间：

c.ChanID | c.name | s.ChanID 
1  | first | 1 
2  | second | NULL  <-- the second and third channels don't match 
3  | third | NULL  <-- to anything in the SUBSCRIBERS table (IS NULL) 
4  | fourth | 4 

Answer 2

SELECT CHANNELS.ChanID FROM CHANNELS 
    LEFT JOIN SUBSCRIBERS ON CHANNELS.ChanID=SUBSCRIBERS.ChanID 
    WHERE 
    CHANNELS.type='public' AND 
    SUBSCRIBERS.nickname='a' 

试试这个

编辑： 我没有得到正确的问题。如果要选择Jonny未订阅的行，请使用像这样的子查询。

SELECT ChanID C FROM CHANNELS WHERE 
(SELECT COUNT(*) FROM SUBSCRIBERS S WHERE S.ChanID=C.ChanID and S.nickname='Jonny') = 0 

Answer 3

select c.ChanID,C.name 
from Channels c Left join subscribers s on 
c.ChanID=s.ChanID 
where s.ChanID is null 

这应该工作的其他条件可能不是必需的。