Question

So, basically, I have a MySQL table called ‘topics’ and another one called ‘replies’, for example. In table ‘topics’, there’s a field called ‘relforum’ which relates this topic to a forum section. And in the table ‘replies’, there’s a field called ‘reltopic’, which relates the reply to a topic. Both tables have an id field, auto_increment primary key.

Now, I want to select all replies from a certain forum. Since ‘replies’ has no ‘relforum’ field, my way would be:

• Select all topics with ‘relforum’ equal to that certain forum and loop through them
• While in the loop, select all replies from the topic that is being ‘processed’ right now
• Merge all fetch_array results in one multidimensional array, then loop through them.

That’s something like this:

$query = mysql_query("SELECT * FROM `topics` WHERE `relforum` = '1'");
while($array = mysql_fetch_array($query)) {
    $temp = mysql_query("SELECT * FROM `replies` WHERE `reltopic` = {$array['id']}");
    $results[] = mysql_fetch_array($temp);
}

Is there a way to merge all that into fewer queries? Because this process would basically run one query per topic in that forum plus one. That would be too much 😛

Adding the relforum field to the replies table is a solution (I’m still designing the DB Part so it’s not a problem to add it), but I would like to see if there’s a solution.

I’m really not good at SQL things, I only know the basic SELECT/INSERT/UPDATE, and I usually generate the last two ones using PHPMyAdmin, so… I guess I need some help.

Thanks for reading!

Answer 1

You basically need a join of two tables.

SELECT * FROM `replies`, `topics` WHERE `replies`.`reltopic` = `topics`.`id` AND `topics`.`relforum` = '1';