Thanks! I was looking for this too.
For me to make this work with a Database View, I did like the following example:
1. Created a DB View with one View Table without Where Clause: [sys_user]
2. Created before Query business rule:
var join = current.addJoinQuery('ldap_import', 'user_user_name', 'u_samaccountname');
join.addCondition('sys_created_on', 'ON', 'Today@javascript:gs.beginningOfToday()@javascript:gs.endOfToday()'); //INNER JOIN
current.addQuery('user_active', 'true'); //ADD where clause to [sys_user]
current.addEncodedQuery("NQuser_user_nameISNOTEMPTY^user_active=true"); //LEFT JOIN
