MySQL 5.6

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CREATE TABLE IF NOT EXISTS `purchases` (
  `name` varchar(150),
  `amount` int(30),
  `city` varchar(30),
  `date` date NOT NULL
);

INSERT INTO `purchases` (`name`, `amount`, `city`, `date`) VALUES
  ('FedEx', '10', 'Chicago', '2020-03-02 10:00:00'),
  ('UPS', '10', 'Atlanta', '2020-03-23 10:00:00'),
  ('USPS', '23', 'Chicago', '2020-04-25 10:00:00'),
  ('FedEx', '39', 'New York', '2020-04-13 10:00:00'),
  ('FedEx', '10', 'Chicago', '2020-04-12 10:00:00'),
  ('UPS', '149', 'Tulsa', '2020-06-12 10:00:00'),
  ('UPS', '145', 'Chicago', '2020-07-15 10:00:00'),
  ('UPS', '152', 'Tulsa', '2020-07-03 10:00:00'),
  ('UPS', '147', 'New York', '2020-07-04 10:00:00'),
  ('FexEd', '122', 'Tulsa', '2020-06-03 10:00:00');
SELECT t.city, t.total period1, COALESCE(SUM(p.amount), 0) period2
FROM (
  SELECT city, SUM(amount) AS total 
  FROM purchases 
  WHERE date BETWEEN '2020-07-01' AND '2020-10-31' 
  GROUP BY city 
  ORDER BY total DESC LIMIT 3
) t LEFT JOIN (
  SELECT city, amount
  FROM purchases
  WHERE date BETWEEN '2020-03-01' AND '2020-06-30'
) p ON p.city = t.city
GROUP BY t.city, t.total
ORDER BY t.total DESC;


city
period1
period2


Tulsa
152
271

New York
147
39

Chicago
145
43


SELECT city,
       SUM(CASE WHEN date BETWEEN '2020-07-01' AND '2020-10-31' THEN amount ELSE 0 END) period1,
       SUM(CASE WHEN date BETWEEN '2020-03-01' AND '2020-06-30' THEN amount ELSE 0 END) period2
FROM purchases
GROUP BY city
ORDER BY period1 DESC LIMIT 3;


city
period1
period2


Tulsa
152
271

New York
147
39

Chicago
145
43


SELECT city,
       SUM(CASE WHEN date >= '2020-07-01' THEN amount ELSE 0 END) period1,
       SUM(CASE WHEN date < '2020-07-01' THEN amount ELSE 0 END) period2
FROM purchases
WHERE date BETWEEN '2020-03-01' AND '2020-10-31'
GROUP BY city
ORDER BY period1 DESC LIMIT 3;


city
period1
period2


Tulsa
152
271

New York
147
39

Chicago
145
43