I often forget the exact syntax of things like this… So here’s an example…

$query1 = 'SELECT * FROM `'.$dbName.'`.`users` WHERE email NOT IN (SELECT email FROM `'.$setupDBName.'`.`users`)';

From Mark Jackson

Also the ‘IN’ and ‘NOT IN’ can be used to specify multiple conditional values – for example:

SELECT * FROM users WHERE email IN (‘[email protected]’,'[email protected]’,'[email protected]’,'[email protected]’);

Saves a bit of time writing it out in full with loads of email = ‘…’ OR email = ‘…’