Done Mock SQL2

Product Sales Analysis III.sql

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+-- # Write your MySQL query statement below
+-- select s1.product_id, s2.first_year, quantity, price 
+-- from Sales s1 join (
+--     select product_id, min(year) as first_year from Sales 
+--     group by product_id
+--     ) s2
+-- on s1.product_id = s2.product_id and s1.year = s2.first_year 
+
+select product_id, year as first_year, quantity, price from Sales 
+where (product_id, year) in (select product_id, min(year) as year from Sales group by product_id)

Customers Who Bought All Products.sql

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+SELECT customer_id 
+FROM Customer 
+GROUP BY customer_id
+HAVING COUNT(DISTINCT product_key) = (SELECT COUNT(DISTINCT product_key) FROM Product)