SQL6 Submitted

Problem1.sql

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+SELECT a.player_id, a.device_id 
+FROM activity a 
+where a.event_date IN (SELECT MIN(b.event_date) FROM activity b WHERE a.player_id = b.player_id)

Problem2.sql

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+SELECT player_id, event_date, SUM(games_played) 
+OVER(PARTITION BY player_id ORDER BY event_date) AS 'games_played_so_far'
+FROM activity

Problem3.sql

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+SELECT ROUND(MIN(SQRT(pow(p2.x-p1.x,2) + pow(p2.y-p1.y,2))),2) as 'shortest' from 
+point2D p1 INNER JOIN point2D p2 
+ON (p1.x, p1.y) < (p2.x, p2.y);

Problem4.sql

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+SELECT p.firstName, p.lastName, a.city, a.state from Person p LEFT JOIN Address a ON p.personId = a.personId

Problem5.sql

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+WITH CTE AS(
+SELECT customer_id , YEAR(order_date) as 'year', SUM(price) as 'price' from orders GROUP BY year , customer_id 
+order by customer_id , year
+)
+
+SELECT c1.customer_id   from CTE c1 LEFT JOIN CTE c2 ON c1.customer_id = c2.customer_id 
+AND c1.year + 1 = c2.year AND c1.price < c2.price GROUP BY c1.customer_id 
+HAVING COUNT(*) - COUNT(c2.customer_id) = 1;