task: #1393

Author: Ivanbyone

README.md

@@ -171,6 +171,7 @@ Useful for preparing for technical interviews and improving your SQL skills.
     - [1204. Last Person to Fit in the Bus](./leetcode/medium/1204.%20Last%20Person%20to%20Fit%20in%20the%20Bus.sql)
     - [1321. Restaurant Growth](./leetcode/medium/1321.%20Restaurant%20Growth.sql)
     - [1341. Movie Rating](./leetcode/medium/1341.%20Movie%20Rating.sql)
+    - [1393. Capital Gain/Loss](./leetcode/medium/1393.%20Capital%20Gain&Loss.sql)
     - [1907. Count Salary Categories](./leetcode/medium/1907.%20Count%20Salary%20Categories.sql)
     - [1934. Confirmation Rate](./leetcode/medium/1934.%20Confirmation%20Rate.sql)
     - [3475. DNA Pattern Recognition](./leetcode/medium/3475.%20DNA%20Pattern%20Recognition.sql)

leetcode/medium/1393. Capital Gain&Loss.sql

@@ -0,0 +1,43 @@
+/*
+Question 1393. Capital Gain/Loss
+Link: https://leetcode.com/problems/capital-gainloss/description/?envType=problem-list-v2&envId=database
+
+Table: Stocks
+
++---------------+---------+
+| Column Name   | Type    |
++---------------+---------+
+| stock_name    | varchar |
+| operation     | enum    |
+| operation_day | int     |
+| price         | int     |
++---------------+---------+
+(stock_name, operation_day) is the primary key (combination of columns with unique values) for this table.
+The operation column is an ENUM (category) of type ('Sell', 'Buy')
+Each row of this table indicates that the stock which has stock_name had an operation on the day operation_day with the price.
+It is guaranteed that each 'Sell' operation for a stock has a corresponding 'Buy' operation in a previous day. It is also guaranteed that each 'Buy' operation for a stock has a corresponding 'Sell' operation in an upcoming day.
+ 
+
+Write a solution to report the Capital gain/loss for each stock.
+
+The Capital gain/loss of a stock is the total gain or loss after buying and selling the stock one or many times.
+
+Return the result table in any order.
+*/
+
+-- with subqueries
+
+SELECT DISTINCT
+    s.stock_name,
+    (
+        SELECT SUM(s1.price)
+        FROM Stocks AS s1
+        WHERE s1.stock_name = s.stock_name AND s1.operation = 'Sell'
+    )
+    - (
+        SELECT SUM(s2.price)
+        FROM Stocks AS s2
+        WHERE s2.stock_name = s.stock_name AND s2.operation = 'Buy'
+    )
+    AS capital_gain_loss
+FROM Stocks AS s