// Data for clients.
$sql = "select coalesce(c.name, 'NULL') as name, sum(time_to_sec(l.duration)) as time from tt_log l
left join tt_clients c on (c.id = l.client_id)
// Data for clients.
$sql = "select coalesce(c.name, 'NULL') as name, sum(time_to_sec(l.duration)) as time from tt_log l
left join tt_clients c on (c.id = l.client_id)