I was working on a Drupal migration project today using the Migrate module where I needed to import only select user roles from the source (Drupal 6) database.
The Migrate module allows for a custom query to select only the user roles that need to be imported. In my case, the two roles I wanted to import had role IDs of 4 and 6. So, how do I write a query using the Drupal Database API to do this? Turns out there's a pretty elegant answer. Rather than writing something like:
SELECT * FROM role r WHERE rid=4 OR rid=6;
The proper way of writing the select query is:
$query = parent::query();
$ored = db_or();
Note the elegant "db_or()" function that returns a DatabaseCondition object. Add the two conditions to this object, and they're automagically "or"ed.
I discovered all this via this nice blog post by Rahul Singla.
$query->condition('rid', array(4,6), 'IN');
But yes, the db_and and db_or methods are very useful.
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Yep, "$query->condition('rid', array(4,6), 'IN');" will work as well, but for some reason, I find the db_or method a bit more elegant.