CREATE TABLE t (
product char,
position char,
count INT
);
INSERT into t values
('onion', 'in', 10),
('onion', 'out', 3),
('cucumber', 'in', 30),
('carrot', 'in', 23),
('onion', 'out', 7),
('cucumber', 'out', 12),
('potato', 'in', 80),
('onion', 'in', 21),
('cabbage', 'in', 35),
('carrot', 'out', 12),
('cabbage', 'out', 3),
('mango', 'in', 25),
('onion', 'out', 3),
('potato', 'out', 10),
('apple', 'in', 45),
('cabbage', 'out', 20),
('cucumber', 'in', 81),
('apple', 'out', 7),
('mango', 'in', 13),
('orange', 'in', 75),
('orange', 'out', 75);
SELECT product, SUM(count * (CASE WHEN position = 'in' THEN 1 ELSE -1 END)) AS result
FROM t
GROUP BY product
HAVING result != 0;
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