MySQL选择所有记录，并为每个选择单独的记录-在一个查询中

Question

I believe what I am trying to achieve here is a nested query - however I am unsure how to continue.

I have 2 tables users and notifications what I am doing is querying notifications table to get the details, however I am also LEFT OUTER JOIN on users table to get my user information. What I have is like this :

          USERS TABLE     
| user id | username | user image |


    NOTIFICATIONS TABLE  
| receiver id | sender id |

Just getting the receivers information is not an issue as I user the following query :

SELECT
    notifications.senderID, notifications.receiverID, users.username, users.image
FROM
    notifications
    LEFT OUTER JOIN users ON users.id = notifications.receiverID
WHERE notifications.receiverID = ' xxx '

What I need to add is a way to foreach record found also grab the users.username and users.image for THAT record ( which will correspond on users.id for notifications.senderID ) as well as for the main record( notifications.recieverID )

IF POSSIBLE I wanted to keep this in one query and outside of a PHP foreach loop.

Answer 1

Join the users table twice with differant alias names

SELECT notifications.senderID, notifications.receiverID, 
       receiver.username as receiver_name, receiver.image as receiver_image,
       sender.username as sender_name, sender.image as sender_image
FROM notifications
LEFT OUTER JOIN users as receiver ON receiver.id = notifications.receiverID
LEFT OUTER JOIN users as sender ON sender.id = notifications.senderID
WHERE notifications.receiverID = ' xxx '

Answer 2

This is the query for example

SELECT User . id , User . username , User . password , User . email , User . role , User . created , User . modified , Userdetail . user_id , Userdetail . first_name , last name , Userdetail . address , Userdetail . telephone FROM cakephp_test . users AS User LEFT JOIN cakephp_test . userdetails AS Userdetail ON ( Userdetail . user_id = User . id ) WHERE User . id = 51 LIMIT 1

in your case

SELECT notifications.senderID, notifications.receiverID, users.username, users.image FROM database_name.users AS User LEFT JOIN database_name.notification AS notification ON (users.id = notifications.receiverID) WHERE User.id = 'xxx' LIMIT 1