SQL 2 Done

Problem1.sql

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+SELECT score , 
+DENSE_RANK() OVER(ORDER BY score DESC) as "rank" 
+FROM Scores ;

Problem2.sql

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+SELECT 
+CASE 
+    WHEN id = ( SELECT MAX(id) FROM Seat ) AND MOD(id,2) = 1 THEN id
+    WHEN MOD(id,2) = 1 THEN id + 1
+    ELSE id - 1 
+END as "id", student
+FROM Seat
+ORDER BY id ;

Problem3.sql

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+SELECT id,
+CASE WHEN p_id IS NULL THEN 'Root'
+WHEN id IN (SELECT p_id FROM Tree WHERE p_id IS NOT NULL) AND p_id IS NOT NULL THEN 'Inner'
+ELSE 'Leaf'
+END as 'type'
+FROM Tree

Problem4.sql

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+WITH CTE AS ( SELECT d.name AS Department, e.name AS Employee, e.salary AS Salary,
+DENSE_RANK() OVER ( PARTITION BY d.name ORDER BY e.salary DESC ) AS 'rnk'
+FROM Employee e
+LEFT JOIN Department d ON d.id = e.departmentId 
+GROUP BY Department, Employee)
+
+SELECT Department, Employee, Salary FROM CTE
+WHERE rnk < 4