Complicated Query

[chibineku]

I am a little baffled by this query:

$verify_sql = "SELECT ft.topic_id, ft.topic_title FROM forum_posts AS fp LEFT JOIN forum_topics AS ft ON fp.topic_id = ft.topic_id WHERE fp.post_id = '".$_GET["post_id"]."'";

Obviously I have two tables, one called forum_topics and one call forum_posts, and there are some PHP elements, but the workings of the query are not explained in the book from which this example comes. I understand how everything else works, though, but the author does not explain this query, merely calling it complicated looking...

[justsomeguy]

It's doing a left join, so it's going to select the records from the forum_posts table and, if there are matching records from the forum_topics table for that post, it will also select those matching records. It's not returning anything from the forum_posts table, but it looks like it's trying to look up a certain post ID, so it's getting information about the topic for that post. Look up SQL joins if you want more information about how they work.

[chibineku]

I understand basic joins, though I can never remember them without looking them up, but it's the fp / ft business. I guess one stands for forum_topics and the other for forum_posts, but I wasn't aware it was necesary to create new names like that.

[justsomeguy]

It's not necessary, it's just an alias if you don't want to keep typing the full name.