Re: mysql case statement

On Monday 28 June 2010 09:49:55 Andrew Ballard wrote: > On Sun, Jun 27, 2010 at 4:08 AM, Tanel Tammik <keevitaja@gmail.com> wrote: > > Hello, > > > > how to select only if value is present? > > > > $query = $db->query("select menus.id, menus.name, > > case > > when panels.id is not null then '1' > > end as hiddenpanel > > > > from " . \DB_MENUS . " as menus > > left join " . \DB_HIDDENPANELS . " as panels on (menus.id = > > panels.menu_id) > > where menus.id='" . (int)$id . "' > > "); > > > > i would like to select hiddenpanel only if there is a corresponding value > > in DB_HIDDENPANELS. At the moment i get NULL if there is no corresponding > > value in HIDDENPANELS table! > > > > Br > > Tanel > > That's what a LEFT JOIN does - it returns all rows from the LEFT table > that match the criteria in the WHERE clause, and then returns any rows > from the RIGHT table that happen do match. If you only want rows that > exist in both tables, change the join from LEFT (OUTER) JOIN to INNER > JOIN. Tanel, we both learned something. I didn't fully understand join myself yet, but I think I do now. but let me ask this if the join wasn't there would an if statement like I mentioned have worked? Blessings, David M.