Added solutions for Mock-SQL-3

Market_Analysis_II.sql

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+# Write your MySQL query statement below
+with users_fav_brand as 
+(
+    select 
+        u.user_id
+        , i.item_id as fav_brand_id
+    from 
+        Users u left join Items i on u.favorite_brand = i.item_brand
+)
+, ranked_orders as
+(
+    select
+        seller_id
+        , item_id
+        , order_date
+        , rank() over(partition by seller_id order by order_date) as rnk
+    from 
+        Orders
+)
+, second_orders as
+(
+    select
+        seller_id
+        , item_id
+    from 
+        ranked_orders
+    where rnk = 2
+)
+, combinations_match as 
+(
+select 
+    u.user_id
+    , u.fav_brand_id
+    , s.item_id
+from
+    users_fav_brand u left join second_orders s on u.user_id = s.seller_id
+where u.fav_brand_id = s.item_id
+)
+select 
+    u.user_id as seller_id
+    , coalesce(case when c.fav_brand_id = c.item_id then 'yes' else null end, 'no') as 2nd_item_fav_brand
+from 
+    Users u left join combinations_match c on u.user_id = c.user_id

Tournament_winners.sql

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+with master_table as 
+(
+    select 
+        first_player as player
+        , first_score as score
+    from 
+        Matches
+    union all
+    select 
+        second_player as player
+        , second_score as score
+    from 
+        Matches
+)
+, player_score_count as
+(
+    select 
+        player
+        , sum(score) as total_score
+    from 
+        master_table
+    group by 1
+)
+, player_group_total as
+(
+select 
+   pc.player as player_id
+   , pc.total_score
+   , p.group_id
+from 
+    player_score_count pc join Players p on pc.player = p.player_id
+)
+, player_group_ranking as
+(
+    select 
+        player_id
+        , group_id
+        , row_number() over(partition by group_id order by total_score desc, player_id asc) as rownum
+    from 
+        player_group_total
+)
+
+select 
+    player_id
+    , group_id
+from 
+    player_group_ranking
+where 
+    rownum = 1