Question

Let’s say that we have a users table, and a user can have many posts (posts have the user_id column).

I want to retrieve posts for the first 5 users, but only one post per user. So, at the end I want to have 5 posts, where each post belongs to a different user. How can I do that in SQL?

Answer 1

You should have two tables

Table : users ; Columns : users_id , user_name
Table2: posts ; Columns : post_id , post_description , users_id

And now to retrieve all user with one post for each

SELECT * FROM users as u
LEFT JOIN (SELECT * FROM posts LIMIT 1)  as p on p.users_id = u.users_id
LIMIT 5 ORDER BY ASC

If you want to get the oldest post for each user

SELECT * FROM users as u
LEFT JOIN (
    SELECT 
        MIN(post_id) as post_id , 
        post_description , 
        users_id  FROM posts
    )  as p on p.users_id = u.users_id
LIMIT 5 ORDER BY ASC

And for latest post use MAX(post_id) instead of MIN(post_id)