如何編寫一個Sql查詢來查找另一個表中的所有參與行？

Question

有3個表格：事件，事件客戶端和客戶端。

編寫一個查詢，查找所有客戶端都有權訪問的事件？

內連接並不保證表中的所有行參加所以這並不能幫助：

select * from events e 
inner join eventclients ec on e.id = ec.eventid 
inner join clients c on etc.clientid = c.id 

Answer 1

您可以使用嵌套NOT EXISTS進行檢查：

SELECT e.* 
FROM events e 
WHERE NOT EXISTS(
    SELECT 1 FROM client c 
    WHERE NOT EXISTS(
     SELECT 1 FROM eventclients ec 
     WHERE ec.eventid = e.id AND c.id= ec.clientid 
    ) 
) 

Demo

Answer 2

假設你的意思是事件有一個多對多的關係客戶端和event_client是它們之間的橋接表，那麼您應該提出關於跨多對多關係的SQL連接的許多其他問題。

SQL many to many select

How to filter SQL results in a has-many-through relation

Answer 3

你也可以做

SELECT e.id, e.name 
    FROM events e LEFT JOIN eventclients ec 
    ON e.id = ec.eventid LEFT JOIN clients c 
    ON ec.clientid = c.id 
GROUP BY e.id, e.name 
HAVING COUNT(ec.clientid) = 
(
    SELECT COUNT(*) FROM clients 
) 

這裏是SQLFiddle演示