SQL4 problems solved

friend_requests_II

@@ -0,0 +1,20 @@
+WITH cte AS(
+    SELECT  id,
+            SUM(num) AS num
+    FROM (
+        SELECT  requester_id AS id,
+                COUNT(*) AS num
+        FROM requestaccepted
+        GROUP BY 1
+        UNION ALL
+        SELECT  accepter_id AS id,
+                COUNT(*) AS num
+        FROM requestaccepted
+        GROUP BY 1
+        )a
+    GROUP BY id
+    )
+SELECT  id,
+        num
+FROM cte
+WHERE num = (SELECT MAX(num) FROM cte);

league_stats

@@ -0,0 +1,37 @@
+SELECT  t.team_name,
+        SUM(matches_played) AS matches_played,
+        SUM(a.points) AS points,
+        SUM(a.goal_for) AS goal_for,
+        SUM(a.goal_against) AS goal_against,
+        SUM(a.goal_for) - SUM(a.goal_against) AS goal_diff
+FROM (
+    -- calculate the home matches score
+    SELECT  home_team_id AS team_id,
+            COUNT(*) AS matches_played,
+            SUM(CASE 
+                WHEN home_team_goals > away_team_goals THEN 3
+                WHEN home_team_goals < away_team_goals THEN 0
+                WHEN home_team_goals = away_team_goals THEN 1
+            END) AS points,
+            SUM(home_team_goals) AS goal_for,
+            SUM(away_team_goals) AS goal_against
+    FROM matches
+    GROUP BY 1
+    UNION ALL
+    -- calculate the away matches score
+    SELECT  away_team_id AS team_id,
+            COUNT(*) AS matches_played,
+            SUM(CASE 
+                WHEN away_team_goals > home_team_goals THEN 3
+                WHEN away_team_goals < home_team_goals THEN 0
+                WHEN away_team_goals = home_team_goals THEN 1
+            END) AS points,
+            SUM(away_team_goals) AS goal_for,
+            SUM(home_team_goals) AS goal_against
+    FROM matches
+    GROUP BY 1
+) a
+INNER JOIN teams t
+ON t.team_id = a.team_id
+GROUP BY t.team_name
+ORDER BY points DESC, goal_diff DESC, team_name;

num_of_seniors_juniors

@@ -0,0 +1,30 @@
+WITH cte AS (
+    SELECT  employee_id,
+            experience,
+            SUM(salary) AS salary,
+            SUM(salary) OVER(PARTITION BY experience ORDER BY salary, employee_id) AS r_sum
+    FROM candidates
+    -- WHERE experience = 'Senior'
+    GROUP BY 1,2
+),
+senior AS (
+    SELECT  'Senior' AS experience,
+            r_sum
+    FROM cte
+    WHERE experience = 'Senior'
+    AND r_sum <= 70000
+),
+junior AS(
+    SELECT  'Junior' AS experience,
+            r_sum
+    FROM cte
+    WHERE experience = 'Junior'
+    AND r_sum <= (SELECT 70000-IFNULL(MAX(r_sum),0) FROM senior)
+)
+SELECT  experience,
+        COUNT(*) AS accepted_candidates
+FROM senior
+UNION ALL 
+SELECT  experience,
+        COUNT(*) AS accepted_candidates
+FROM junior;

sales_person

@@ -0,0 +1,12 @@
+WITH cte AS (
+    SELECT  o.com_id,
+        o.sales_id,
+        c.name
+FROM orders o
+INNER JOIN company c
+ON o.com_id = c.com_id
+WHERE c.name = 'RED'
+)
+SELECT  name
+FROM salesperson
+WHERE sales_id NOT IN (SELECT DISTINCT sales_id FROM cte);