Wenn Sie in der Hauptabfrage mehrere Joins verwenden, erhalten Sie am Ende ein Kreuzprodukt aller Tabellen, sodass die Summen mit der Anzahl der übereinstimmenden Zeilen in einer anderen Tabelle multipliziert werden. Sie müssen die Summen in Unterabfragen verschieben.
SELECT last_name, first_name, DATE_FORMAT(LEAST(mil_date, tm_date), '%m/%d/%y' ) AS dates,
total, minutes
FROM bhds_teachers AS i
LEFT JOIN (
SELECT ds_id, YEARWEEK(mil_date) AS week, MIN(mil_date) AS mil_date, SUM(drive_time) AS minutes
FROM bhds_mileage
WHERE mil_date BETWEEN '2016-04-11' AND '2016-04-30'
AND bhds_mileage.ds_id = 5
GROUP BY ds_id, week) AS m
ON m.ds_id = i.ds_id
LEFT JOIN (
SELECT ds_id, YEARWEEK(tm_date) AS week, MIN(tm_date) AS tm_date, SUM(tm_hours) AS total
WHERE tm_date BETWEEN '2016-04-11' AND '2016-04-30' AND bhds_timecard.ds_id = 5
GROUP BY ds_id, week) AS t
ON t.ds_id = i.ds_id AND t.week = m.week
