difference between hours, MySQL

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#MySQL 5.7.12
#please drop objects you've created at the end of the script 
#or check for their existance before creating
#'\\' is a delimiter

CREATE TABLE tableA
    (`datetime` datetime, `energy` int)
;
    
INSERT INTO tableA
    (`datetime`, `energy`)
VALUES
    ('2010-06-15 10:00:00', 1),
    ('2010-06-15 10:15:00', 3),
    ('2010-06-15 10:30:00', 6),
    ('2010-06-15 10:45:00', 7),
    ('2010-06-15 11:00:00', 9),
    ('2010-06-15 11:15:00', 12),
    ('2010-06-15 11:30:00', 15),
    ('2010-06-15 11:45:00', 28),
    ('2010-06-15 12:00:00', 52),
    ('2010-06-15 12:15:00', 75),
    ('2010-06-15 12:30:00', 88),
    ('2010-06-15 12:45:00', 102),
    ('2010-06-15 13:00:00', 150),
    ('2010-06-15 13:15:00', 189),
    ('2010-06-15 13:30:00', 200),
    ('2010-06-15 13:45:00', 205),
    ('2010-06-15 14:00:00', 209),
    ('2010-06-15 14:15:00', 400),
    ('2010-06-15 14:30:00', 450),
    ('2010-06-15 14:45:00', 480),
    ('2010-06-15 15:00:00', 500)
;

SELECT a.datetime, b.energy - a.energy AS energy
FROM tableA AS a
JOIN TableA AS b ON a.datetime = DATE_SUB(b.datetime, INTERVAL 1 HOUR)
WHERE MINUTE(a.datetime) = 0;

DROP TABLE tableA;


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