I am building a custom forum application with CodeIgniter. I have 4 primary tables: parents(categories), children(boards), threads, and messages(thread replies). What I would like to do is display the information of the latest post from a certain board... this will be on the index page of the forums. Here's what my tables look like. I won't list the category table since we won't be using that one for this feature.

| Table: Children ---|
|--------------------|
| child_id (int, 15) |
|--------------------|
| title (varchar, 65 |
|--------------------|

| Table: threads ----|
|--------------------|
| thread_id (int, 15)|
|--------------------|
| first_msg_id(int, 15) 
|--------------------|
| author_id(int, 15) |
|--------------------|
| title(varchar, 65) |
|--------------------|

| Table: messages ---|
|--------------------|
| message_id(int, 15)|
|--------------------|
| thread_id(int, 15) |
|--------------------|
| author_id(int, 15) |
|--------------------|

I was wondering if you guys could give me some ideas of how to use joins to do this? I have no idea where to start, else I would have given you some code... lol. Thanks for your time.

Update

So I figured I would at least make an attempt at this, but I got as far as SELECT, and then had no idea about the left joins. Here's what I have so far...

$query = "
                    SELECT
                        m.message_id AS m_id, m.author_id, m.thread_id AS mt_id
                        t.thread_id AS t_id, t.child_id AS tc_id
                    FROM forum_messages AS m
                    WHERE t.child_id = ".$board_id."
                        LEFT JOIN "

The "Children" table

The threads table

The messages table