SELECT

    IF(invoice.paid=0,'unbilled',IF(invoice.paid=1,'paid','unpaid')) AS status,
   -- IFNULL(SUM(tasks.task_hours),0) AS project_hours,
   -- IFNULL(FORMAT(SUM(tasks.fee),2),0) AS project_fee
    ROUND(IF(tt.general_time_flag=1,pr.hourly_rate,tk.fee)*IFNULL(SUM(TIME_TO_SEC(TIMEDIFF(IF(tt.end_time='0000-00-00 00:00:00',now(),tt.end_time), tt.start_time)))/3600,0),2) AS project_fee,
    
    ROUND(SUM(TIME_TO_SEC(TIMEDIFF(IF(tt.end_time='0000-00-00 00:00:00',now(),tt.end_time), tt.start_time)))/3600,2) AS project_hours
    
FROM

    time_tracker AS tt
        LEFT JOIN
    tasks AS tk ON tt.element_id = tk.task_id AND tt.element_type=2
        LEFT JOIN
    projects AS pr ON tt.element_id = pr.project_id AND tt.element_type=1,
    
    invoice_task ,
    invoice

WHERE

    
    invoice.invoice_id = invoice_task.invoice_id
    AND invoice_task.task_id = tk.task_id
    ##DATES##
    
GROUP BY invoice.paid