Re: discussion forum from j. meloni's book

Jennifer Goodie" <goodie@apollointeractive.com> writes: > You didn't switch the aliases around, you just switched the join order. > This will provide unexpected results. In order to understand it, you should > read up on left joins. > http://www.mysql.com/doc/en/JOIN.html ............................ Thank you. But... // the query $verify = "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]"; ........................... My question: why - or how can - the columns ft.topic_id and ft.topic_title come from the table forum_posts? In the original schema, there is no column called topic_title in the table called forum_posts. When I change the following to read: $verify = "select ft.topic_id, ft.topic_title from forum_topics as ft left join forum_posts as fp on fp.topic_id = ft.topic_id where fp.post_id = $_GET[post_id]"; It works fine. /*Roughly translated: Select the column ft.topic_id along with the column ft.topic_title from the table called forum_topics which we'll call ft. Then join the table called forum_topics onto the table called forum_posts and match the records where topic_id corresponds in both tables along with post_id corresponds in both tables.*/