Some list vendors will often sell low-quality dialer lists with a lot of missing information. As an example, here is a command to delete all records with missing Last Name field within the list ‘123’. You can permutate last with first or any other column:
DELETE from vicidial_list WHERE list_id='123' AND last_name='';
To run a similar query which would delete all records with a certain string in the Last Name field within the same list, use the following SQL:
DELETE from vicidial_list where list_id='123' and (last_name LIKE '%is_name%' OR first_name LIKE '%STRING_HERE%');