diff --git a/Department_top3_Salaries.sql b/Department_top3_Salaries.sql
new file mode 100644
index 0000000..aa6ac0e
--- /dev/null
+++ b/Department_top3_Salaries.sql
@@ -0,0 +1,5 @@
+WITH CTE as(
+    SELECT d.name as 'department',d.id as'did', e.name as 'employee', e.salary as 'salary' from employee e left join department d ON e.departmentId = d.id
+)
+SELECT department, employee, salary from CTE c
+where 3> (Select count(DISTINCT e2.salary)from employee e2 where c.did = e2.departmentId and e2.salary>c.salary)
\ No newline at end of file
diff --git a/ExchangeSeats.sql b/ExchangeSeats.sql
new file mode 100644
index 0000000..3f63361
--- /dev/null
+++ b/ExchangeSeats.sql
@@ -0,0 +1,9 @@
+SELECT(
+    CASE
+    WHEN MOD(id,2) !=0 AND id = cnts THEN id
+    WHEN MOD(id,2) !=0 AND id !=cnts THEN id+1
+    ELSE id-1
+    END
+) as 'id', student from seat,
+(SELECT COUNT(*) AS 'cnts' from seat) as seat_counts
+ORDER BY id
\ No newline at end of file
diff --git a/RankScores.sql b/RankScores.sql
new file mode 100644
index 0000000..578adbd
--- /dev/null
+++ b/RankScores.sql
@@ -0,0 +1,5 @@
+SELECT s1.score,
+(SELECT COUNT(DISTINCT s2.score) FROM scores s2
+WHERE s2.score>=s1.score)
+AS 'rank' FROM scores s1
+ORDER BY s1.score DESC;
\ No newline at end of file
diff --git a/TreeNode.sql b/TreeNode.sql
new file mode 100644
index 0000000..02854b8
--- /dev/null
+++ b/TreeNode.sql
@@ -0,0 +1,6 @@
+SELECT id, 'Root' as type from tree where p_id is null
+UNION
+Select id, 'Leaf' as type from tree where id NOT IN (Select Distinct p_id from tree where p_id is not null) And p_id is not null
+UNION
+Select id, 'Inner' as type from tree where id IN (Select Distinct p_id from tree where p_id is not null) And p_id is not null
+Order by id
\ No newline at end of file