SELECT
    temp.task_id,
    tags.name as task_label,
    task_time_spent,
    task_time_spent / labels as labels_on_task
FROM
(
    SELECT
        task_log.task_id,
        SUM(time_spent) as task_time_spent,
        COUNT(DISTINCT tag_id) as labels
    FROM task_log
    INNER JOIN task_effort on task_effort.task_log_id = task_log.id
    INNER JOIN task_tags on task_tags.task_id = task_log.task_id
    INNER JOIN tags on tags.id = task_tags.tag_id
    GROUP BY task_log.task_id
) AS temp
INNER JOIN task_tags on task_tags.task_id = temp.task_id
INNER JOIN tags on tags.id = task_tags.tag_id
GROUP BY task_label