MySQL 5.6

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CREATE TABLE orders(
   id         INTEGER  NOT NULL PRIMARY KEY 
  ,order_sum  NUMERIC(11,2) NOT NULL
  ,user_id    INTEGER  NOT NULL
  ,created_at VARCHAR(21) NOT NULL
);
INSERT INTO orders(id,order_sum,user_id,created_at) VALUES (1,25.13,7,'2020-01-25 09:13:00');
INSERT INTO orders(id,order_sum,user_id,created_at) VALUES (2,14.00,5,'2020-01-26 10:14:00');
INSERT INTO orders(id,order_sum,user_id,created_at) VALUES (3,35.00,1,'2020-01-27 11:13:00');
CREATE TABLE order_items(
   id          INTEGER  NOT NULL PRIMARY KEY 
  ,order_id    INTEGER  NOT NULL
  ,energy_used INTEGER  NOT NULL
  ,created_at  VARCHAR(21) NOT NULL
);
INSERT INTO order_items(id,order_id,energy_used,created_at) VALUES (1,1,65,'2020-01-25 09:13:00');
INSERT INTO order_items(id,order_id,energy_used,created_at) VALUES (2,1,12,'2020-01-25 09:13:00');
INSERT INTO order_items(id,order_id,energy_used,created_at) VALUES (3,2,70,'2020-01-26 10:14:00');
INSERT INTO order_items(id,order_id,energy_used,created_at) VALUES (4,2,5,'2020-01-26 10:14:00');
INSERT INTO order_items(id,order_id,energy_used,created_at) VALUES (5,3,0,'2020-01-27 11:13:00');
select 
    date(o.created_at) date_of_month,
    i.total_energy_used,
    o.created_at last_order_date,
    o.order_sum last_order_sum
from orders o
inner join (
    select date(o1.created_at) date_of_month, sum(i1.energy_used) total_energy_used
    from orders o1
    inner join order_items i1 on o1.id = i1.order_id
    group by date(o1.created_at)
) i on i.date_of_month = date(o.created_at)
where o.created_at = (
    select max(o1.created_at)
    from orders o1
    where date(o1.created_at) = date(o.created_at)
)


date_of_month
total_energy_used
last_order_date
last_order_sum


2020-01-25
77
2020-01-25 09:13:00
25.13

2020-01-26
75
2020-01-26 10:14:00
14.00

2020-01-27
0
2020-01-27 11:13:00
35.00

date_of_month	total_energy_used	last_order_date	last_order_sum
2020-01-25	77	2020-01-25 09:13:00	25.13
2020-01-26	75	2020-01-26 10:14:00	14.00
2020-01-27	0	2020-01-27 11:13:00	35.00