SQL查詢來獲取未連接的用戶列表

Question

我有兩個表稱爲用戶&連接

我需要獲取用戶列表怎麼沒有從用戶表連接

如用戶ID 1已經發送的請求&連接到4 & 6.如何編寫一個查詢來獲取其他未與userid（1）連接的用戶。

預期結果將是用戶id = 1

2  bb  b@a.com 
3  cc  c@c.com 
5  ff 

答案被理解。

Answer 1

簡單woulb是：

SELECT * from users a 
WHERE userid != :userid 
    AND not exists (select * from connections 
        where (userid = :userid and c_userid = a.userid) 
        or (userid = a.userid and c_userid = :userid)) 

Answer 2

下面將退回沒有在連接表中的所有用戶。

SELECT * FROM users AS u 
    WHERE (SELECT count(*) FROM connections AS c 
     WHERE c.userid=u.userid AND reqType != 0) = 0; 

Answer 3

下面的查詢獲取用戶不是與用戶ID相關聯= 1

select u.userid,u.name,u.email 
from connections 
left join users as u on connections.c_userid = u.userid 
where connections.userid =1 and connections.reqtype in (0,1) 

Answer 4

您嘗試此查詢

select *from users where userid not in (select c_userId from connenctions where where userid=1) and userid!=1