Question

I am trying to make a multi-table query that I am not quite sure how to do properly. I have User, Message, Thread, and Project.

A User is associated with Message/Thread/Project as either the Creator or as it being ‘shared’ with them.

A Message is contained within a Thread (associated by message.thread_id and thread.id), and a Thread is contained within a Project (associated by thread.project_id and project_id).

I would like to create a query where given a User.id value, it will return all messages that the user has access to, as well as the Thread and Project name that that message is under, both as Creator or ‘Shared’. I use a table to handle the ‘shares’. The rough diagram is: http://min.us/mvpqbAU

There are more columns in each, but I left them out for simplicity.

Answer 1

I’ve made some assumptions on column names for message, project_name and thread_name as they are not included in the diagram.

/* Get messages where user is creator */
select u.name, m.message, p.project_name, t.thread_name
    from user u
        inner join message m
            on u.id = m.owner_user_id
        inner join thread t
            on m.group_id = t.id
        inner join project p
            on t.project_id = p.id
    where u.id = @YourUserID
union
/* Get messages where user has shared access */
select u.name, m.message, p.project_name, t.thread_name
    from user u
        inner join message_share ms
            on u.id = ms.user_id
        inner join message m
            on ms.message_id = m.id
                and m.owner_user_id <> @YourUserID
        inner join thread t
            on m.group_id = t.id
        inner join project p
            on t.project_id = p.id
    where u.id = @YourUserID