Completed MockSQL3

01-TournamentWinners.sql

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+-- Problem 1 - Tournament Winners (https://leetcode.com/problems/tournament-winners/description/)
+-- Step 1 - Grouping Players From first_player and second_player columns in Matches
+WITH groupedplayers AS(
+    SELECT first_player AS 'player_id', first_score AS 'score'
+    FROM Matches
+    UNION ALL
+    SELECT second_player AS 'player_id', second_score AS 'score'
+    FROM Matches
+),
+-- Step 2 - Computing total scores of each player
+sumscores AS(
+SELECT player_id, SUM(score) AS 'total_score'
+FROM groupedplayers
+GROUP BY player_id
+),
+-- Step 3 - Ranking Players Based on Score Using DENSE_RANK()
+rankedplayers AS(
+    SELECT p.group_id AS 'group_id', s.player_id AS 'player_id', DENSE_RANK() OVER(PARTITION BY  p.group_id ORDER BY s.total_score DESC, s.player_id) AS 'rnk'
+FROM Players p
+INNER JOIN sumscores s
+ON p.player_id = s.player_id
+GROUP BY p.player_id, p.group_id
+)
+-- Step 4 - Selecting the top player in each group based on score
+SELECT r.group_id, r.player_id
+FROM rankedplayers r
+WHERE rnk = 1;

02-MarketAnalysis-II.sql

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+-- Problem 2 - Market Analysis II - (https://leetcode.com/problems/market-analysis-ii/)
+-- Step 1 - Ordering Items
+WITH ordereditems AS(
+    SELECT o.order_date AS 'order_date', o.seller_id AS 'seller_id', i.item_brand AS 'item_brand'
+    FROM Orders o
+    INNER JOIN Items i
+    ON o.item_id = i.item_id
+),
+-- Step 2 - Favorite Brands of Each User Found
+favbrand AS (
+    SELECT u.user_id AS 'user_id', u.favorite_brand AS 'fav_brand', o.item_brand AS 'item_brand', ROW_NUMBER() OVER(PARTITION BY u.user_id ORDER BY o.order_date) AS 'rnk'
+    FROM Users u
+    INNER JOIN ordereditems o
+    ON u.user_id = o.seller_id
+)
+-- Step 3 - Finding Second Favorite Item of Each User
+SELECT u.user_id AS 'seller_id',
+CASE
+    WHEN f.item_brand = u.favorite_brand THEN 'yes'
+    ELSE 'no'
+END AS '2nd_item_fav_brand'
+FROM Users u
+LEFT JOIN favbrand f
+ON u.user_id = f.user_id 
+AND f.rnk = 2;