如果相关表上存在id，如何查询不包含数据的表？

Question

Here's my tables.

Notification Table

+----+--------------+
| Id | Subject      |
+----+--------------+
| 1  | Loreum Ipsum |
| 2  | Hello World  |
| 3  | Pls Help     |
+----+--------------+

UserNotification Table

+----+----------------+--------+
| Id | NotificationId | Status |
+----+----------------+--------+
| 1  | 1              | Read   |
+----+----------------+--------+

I want to query notification table without including data if NotificationId exists on the UserNotification Table

I want result:

Notification Table

+----+-------------+
| Id | Subject     |
+----+-------------+
| 2  | Hello World |
| 3  | Pls Help    |
+----+-------------+

Answer 1

Use NOT EXISTS

Query

SELECT * FROM Notification n
WHERE NOT EXISTS(
    SELECT 1 FROM UserNotification u
    WHERE n.Id = u.NotificationId
);

sql fiddle demo

Answer 2

You can use not in

select Id,Subject from notificationTable
where Id not in (select Id from userNotificationTable) ;

Answer 3

You also can use JOIN :

SELECT n.*
FROM Notification n
JOIN UserNotification un
ON n.Id <> un.NotificationId

SQLFiddle Demo

Answer 4

You can do something like ..

Select * from Notification
left join UserNotification on Notification.id = UserNotification.NotificationId
where UserNotification.id is null

SQLFiddle

Answer 5

You can achieve this by LEFT JOIN with NULL check:

SELECT N.Id, N.Subject
FROM `Notification` N
LEFT JOIN `UserNotification` U ON U.NotificationId = N.Id
WHERE U.NotificationId IS NULL

Answer 6

Use NOT IN

Select * from Notification where id NOT IN (SELECT id FROM UserNotification)

This sql will help for get data

Answer 7

SELECT n.Id, n.Subject FROM Notification n
LEFT JOIN UserNotification nu on nu.NotificationId = n.id
WHERE nu.id IS NULL

Answer 8

you want to return the notification that are no in usernotification

try this :

select Id,Subject
from Notification  
where 
id not in (
select distinct NotificationId  from UserNotification
)