如何在一个查询中从用户，帖子，评论表中获取结果

Question

The title may not be the fit to the question perfectly ! pardon me

Goal

I want to achieve the name of the user who has done a post ,the description of that post( p_description ), the comments that are there on that post ,and the name of those who has provided comments ( comment_description )

How can I achieve that ?

I've three tables:

user

post and

comments

User table is like :

u_id name and so...

Post table, here it is :

u_id p_id p_description

u_id as foreign key from user table ,

and the Comments table is:

u_id p_id comment_description .

note that the u_id and p_id in table comments are both as foreign keys from table user and post respectively.

I'm writing the following query for the above Goal :

SELECT p_description,f_name,comment_description as COMMENT FROM user JOIN post ON user.u_id = post.u_id JOIN comments ON user.u_id = comments.u_id

It gives me the post description , name of that guy who has done post , and the comments on that post , and I want to have also the name of those guys who has done comments to that post.

If the problem is not explained well.

simply I want query for the above GOAL regarding those three tables.

Answer 1

Join user once more on the user ID in comments .

SELECT u1.name,
       p1.p_description,
       u2.name,
       c1.comment_description
       FROM user u1
            INNER JOIN post p1
                       ON u1.u_id = p1.u_id
            INNER JOIN comments c1
                       ON c1.p_id = p1.p_id
            INNER JOIN user u2
                       ON u2.p_id = c1.p_id;