Optimer query

SELECT DISTINCT u.user_id, CONCAT(fname, ' ', lname) AS full_name
        FROM user AS u
        LEFT JOIN participates AS p
        ON
            p.user_id = u.user_id
            AND
            status != 'STATUS_REJECTED'
        LEFT JOIN appointment AS a
        ON
            p.appointment_id = a.appointment_id
            AND
            ((a.start_time >= '$start_time' AND a.start_time < '$end_time') OR (a.end_time >= '$start_time' AND a.end_time < '$end_time') OR (a.start_time < '$start_time' AND a.end_time > '$end_time'))
            AND
            a.cancelled_time IS NULL
        LEFT JOIN appointment AS ap
        ON
            ap.user_id = u.user_id
            AND
            ((ap.start_time >= '$start_time' AND ap.start_time < '$end_time') OR (ap.end_time >= '$start_time' AND ap.end_time < '$end_time') OR (ap.start_time < '$start_time' AND ap.end_time > '$end_time'))
            AND
            ap.cancelled_time IS NULL
        WHERE
            a.appointment_id IS NULL AND ap.user_id IS NULL   

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Jeg har på fornemmelsen man kan slippe for den sidste LEFT JOIN (LEFT JOIN appointment AS ap).

Er der nogle der kan lure hvordan? Sådan at forspørgslen naturligvis gør det samme som nu.