Done Mock-SQL-3

Market_Analysis_II.sql

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+# Write your MySQL query statement below
+
+WITH CTE AS (
+    SELECT seller_id, item_id, RANK() OVER(PARTITION BY seller_id ORDER BY order_date) AS rnk FROM Orders
+), 
+
+ACTE AS (
+    SELECT CTE.seller_id, Items.item_brand FROM CTE JOIN Items ON CTE.item_id = Items.item_id WHERE rnk = 2
+)
+
+SELECT Users.user_id AS seller_id, IF(Users.favorite_brand = ACTE.item_brand, 'yes', 'no') AS 2nd_item_fav_brand FROM Users LEFT JOIN ACTE ON Users.user_id = ACTE.seller_id;

Tournament_Winners.sql

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+WITH cte 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
+),
+cte2 AS (
+    SELECT  p.player_id,  p.group_id, COALESCE(SUM(c.score), 0) AS total_score FROM Players p
+    LEFT JOIN cte c ON p.player_id = c.player_id
+    GROUP BY p.player_id, p.group_id
+),
+cte3 AS (
+  SELECT *, ROW_NUMBER() OVER (PARTITION BY group_id ORDER BY total_score DESC, player_id ASC
+        ) AS rnk
+  FROM cte2
+)
+SELECT group_id, player_id
+FROM cte3
+WHERE rnk = 1;