Versuchen Sie diese Abfrage -
SELECT
t1.dt AS date,
t1.value - t2.value AS value
FROM
(SELECT DATE(date) dt, MAX(value) value FROM table GROUP BY dt) t1
JOIN
(SELECT DATE(date) dt, MAX(value) value FROM table GROUP BY dt) t2
ON t1.dt = t2.dt + INTERVAL 1 DAY