MockSQL3_Complete_RN32MAY2025DS

Market Analysis II.sql

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+-- Solution for Mock SQL 3 question : Market Analysis II
+-- Method 1
+WITH cnt AS (
+    SELECT  seller_id,
+            COUNT(*) cnt
+    FROM orders
+    GROUP BY seller_id
+),
+main AS (
+SELECT  user_id AS seller_id,
+        2nd_item_fav_brand,
+        rwn
+FROM (
+    SELECT  u.user_id,
+            -- o.order_date,
+            -- i.item_brand,
+            -- u.favorite_brand,
+            CASE
+                WHEN i.item_brand = u.favorite_brand AND c.cnt > 1 THEN 'yes'
+                ELSE 'no'
+            END AS 2nd_item_fav_brand,
+            ROW_NUMBER() OVER(PARTITION BY u.user_id ORDER BY o.order_date) AS rwn
+    FROM users u
+    LEFT JOIN orders o
+    ON o.seller_id = u.user_id
+    LEFT JOIN items i
+    ON o.item_id = i.item_id
+    LEFT JOIN cnt c
+    ON u.user_id = c.seller_id
+    ORDER BY u.user_id, o.order_date
+    ) a
+WHERE rwn IN (1,2)
+)
+SELECT  seller_id,
+        2nd_item_fav_brand
+FROM main
+WHERE (seller_id, rwn) IN (SELECT seller_id, MAX(rwn) FROM main GROUP BY seller_id);
+
+-- Method 2
+WITH cte AS (
+    SELECT  order_date,
+            item_brand,
+            seller_id,
+            RANK() OVER(PARTITION BY o.seller_id ORDER BY o.order_date) AS 'rnk'
+    FROM orders o
+    JOIN items i
+    ON o.item_id = i.item_id
+),
+cte2 AS (
+    SELECT  *
+    FROM cte 
+    WHERE rnk = 2
+)
+SELECT  user_id AS 'seller_id',
+        CASE
+            WHEN rnk = 2 AND item_brand = favorite_brand THEN 'yes'
+            ELSE 'no'
+        END AS '2nd_item_fav_brand'
+FROM users
+LEFT JOIN cte2
+ON cte2.seller_id = users.user_id;

Tournament Winners.sql

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+-- Soution for Mock SQL 3 question: Tournament Winners
+WITH cte AS (
+    SELECT  player_id,
+            SUM(score) AS score
+    FROM (
+        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
+    ) a
+    GROUP BY player_id
+)
+SELECT  group_id,
+        player_id
+FROM (
+    SELECT  p.group_id,
+            c.player_id,
+            c.score,
+            ROW_NUMBER() OVER(PARTITION BY p.group_id ORDER BY c.score DESC, c.player_id) rwn
+            -- order by score desc first so that we consider the max scored player, and then sorting by player_id ascending so that we capture the lowest player_id in case of a tie.
+    FROM players p
+    JOIN cte c
+    ON p.player_id = c.player_id
+) a
+WHERE rwn = 1;