feat: problem 1 and problem 2 added

problem1-2004-seniors-and-juniors.sql

@@ -0,0 +1,34 @@
+with running_sum_salary as (
+    select
+        employee_id,
+        experience,
+        salary,
+        sum(salary)
+            over (
+                partition by experience
+                order by experience desc, salary asc, employee_id asc
+            )
+            as running_sum
+    from
+        candidates
+)
+
+select
+    'Senior' as experience,
+    count(employee_id) as accepted_candidates
+from running_sum_salary
+where running_sum <= 70000 and experience = 'Senior'
+
+union all
+
+select
+    'Junior' as experience,
+    count(employee_id) as accepted_candidates
+from running_sum_salary
+where
+    running_sum
+    <= 70000 - (
+        select coalesce(max(running_sum), 0) from running_sum_salary
+        where running_sum <= 70000 and experience = 'Senior'
+    )
+    and experience = 'Junior'

problem2-1841-league-stattistics.sql

@@ -0,0 +1,42 @@
+with team_stats_pivot as (
+    select
+        home_team_id as team,
+        home_team_goals as goal_for,
+        away_team_goals as goal_against,
+        case
+            when home_team_goals > away_team_goals then 3
+            when home_team_goals < away_team_goals then 0
+            else
+                1
+        end as 'points'
+    from matches
+
+    union all
+
+    select
+        away_team_id as team,
+        away_team_goals as goal_for,
+        home_team_goals as goal_against,
+        case
+            when away_team_goals > home_team_goals then 3
+            when away_team_goals < home_team_goals then 0
+            else
+                1
+        end as 'points'
+    from matches
+
+)
+
+select
+    teams.team_name,
+    count(ts.team) as matches_played,
+    sum(ts.points) as points,
+    sum(ts.goal_for) as goal_for,
+    sum(ts.goal_against) as goal_against,
+    sum(ts.goal_for) - sum(ts.goal_against) as goal_diff
+from team_stats_pivot as ts
+inner join
+    teams
+    on ts.team = teams.team_id
+group by team
+order by points desc, goal_diff desc, team_name asc

problem3-607-sales-person.sql

@@ -0,0 +1,8 @@
+SELECT s.name
+FROM salesperson AS s
+WHERE s.sales_id NOT IN (
+    SELECT o.sales_id
+    FROM orders AS o
+    INNER JOIN company AS c ON o.com_id = c.com_id
+    WHERE c.name = 'RED'
+)

problem4-602-friend-request.sql

@@ -0,0 +1,15 @@
+with cte_friends as (
+    select requester_id as id
+    from requestaccepted
+    union all
+    select accepter_id as id
+    from requestaccepted
+)
+
+select distinct
+    id,
+    count(id) as num
+from cte_friends
+group by id
+order by num desc
+limit 1