LeetCode 1393. Capital Gain/Loss

問題：計算買賣損失

解法：透過SUM搭配CASE WHEN即可

SELECT stock_name,
       SUM(
               CASE
                   WHEN operation = 'Buy' THEN -1 * price
                   WHEN operation = 'sell' THEN price
                   END
           ) AS capital_gain_loss
FROM Stocks
GROUP BY stock_name;