2x rozdílné count přes JOIN

SELECT a.*,
            IFNULL(COUNT(b.task_id),0) AS tasks_sum,
            IFNULL(COUNT(c.task_id),0) AS tasks_finished,
            ( UNIX_TIMESTAMP(NOW()) - UNIX_TIMESTAMP(a.created) ) / ( UNIX_TIMESTAMP(a.deadline) - UNIX_TIMESTAMP(a.created) ) * 100 AS percentage
          FROM `projects` a
          LEFT JOIN projects_tasks b
            ON b.project_id=a.project_id
          LEFT JOIN projects_tasks c
            ON (c.project_id=a.project_id AND c.status='finished')
          WHERE a.status<>'finished'
          GROUP BY a.project_id
          ORDER BY a.deadline ASC