mysql if row doesn't exist, grab default value

Question

I\'m making a preferences module for a system so users can define their own preferences for certain parts (stuff like lay-out, color-scheme, homescreen etc.). Every preferen

Answer 1

WHERE (user_id = 17 OR user_id IS NULL) AND name = "menu_items"

And just to clean up the rest of the query:

The id in preferences defined doesn't need to be there, use a combined key of preference_id and user_id instead.

If the id of preferences was named preference_id, the long ON statement could be replaced with USING(preference_id)

The IF function can be replaced with COALESCE(defined_value, default_value)

Answer 2

If I where you I would do one/two queries.

So you would get:

$query = "SELECT * FROM preferences_defined WHERE user_id = 17 AND name = 'menu_items'"

And then in PHP:

$rows = mysql_num_rows($query);
if($rows == 0){
$query = "SELECT * FROM preferences WHERE name = 'menu_items'"}

This way your right query will always be in the $query var. Hope this helps!