diff --git a/Department_Salary1 - Copy (2).sql b/Department_Salary1 - Copy (2).sql
new file mode 100644
index 0000000..780cf2a
--- /dev/null
+++ b/Department_Salary1 - Copy (2).sql	
@@ -0,0 +1,5 @@
+# Write your MySQL query statement below
+WITH CTE AS(
+    SELECT D.NAME AS DEPARTMENT, E.NAME, E.SALARY, DENSE_RANK() OVER (PARTITION BY E.DEPARTMENTID ORDER BY E.SALARY DESC) AS RNK FROM EMPLOYEE E INNER JOIN DEPARTMENT D ON E.DEPARTMENTID = D.ID
+)
+SELECT DEPARTMENT, NAME AS EMPLOYEE, SALARY FROM CTE WHERE RNK <=3;
\ No newline at end of file
diff --git a/Department_Salary1 - Copy.sql b/Department_Salary1 - Copy.sql
new file mode 100644
index 0000000..780cf2a
--- /dev/null
+++ b/Department_Salary1 - Copy.sql	
@@ -0,0 +1,5 @@
+# Write your MySQL query statement below
+WITH CTE AS(
+    SELECT D.NAME AS DEPARTMENT, E.NAME, E.SALARY, DENSE_RANK() OVER (PARTITION BY E.DEPARTMENTID ORDER BY E.SALARY DESC) AS RNK FROM EMPLOYEE E INNER JOIN DEPARTMENT D ON E.DEPARTMENTID = D.ID
+)
+SELECT DEPARTMENT, NAME AS EMPLOYEE, SALARY FROM CTE WHERE RNK <=3;
\ No newline at end of file
diff --git a/Department_Salary1.sql b/Department_Salary1.sql
new file mode 100644
index 0000000..780cf2a
--- /dev/null
+++ b/Department_Salary1.sql
@@ -0,0 +1,5 @@
+# Write your MySQL query statement below
+WITH CTE AS(
+    SELECT D.NAME AS DEPARTMENT, E.NAME, E.SALARY, DENSE_RANK() OVER (PARTITION BY E.DEPARTMENTID ORDER BY E.SALARY DESC) AS RNK FROM EMPLOYEE E INNER JOIN DEPARTMENT D ON E.DEPARTMENTID = D.ID
+)
+SELECT DEPARTMENT, NAME AS EMPLOYEE, SALARY FROM CTE WHERE RNK <=3;
\ No newline at end of file
diff --git a/Rank_Score.sql b/Rank_Score.sql
new file mode 100644
index 0000000..2d04159
--- /dev/null
+++ b/Rank_Score.sql
@@ -0,0 +1 @@
+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/Swap Seat.sql b/Swap Seat.sql
new file mode 100644
index 0000000..b3e8434
--- /dev/null
+++ b/Swap Seat.sql	
@@ -0,0 +1,7 @@
+# Write your MySQL query statement below
+SELECT (
+    CASE 
+    WHEN MOD(S.ID,2) !=0 AND S.ID != C.CNT THEN S.ID + 1
+    WHEN MOD(S.ID,2) !=0 AND S.ID = C.CNT THEN S.ID
+    ELSE S.ID - 1
+END) AS ID, S.STUDENT FROM SEAT S, (SELECT COUNT(*) AS CNT FROM SEAT ORDER BY ID) AS C ORDER BY ID;
\ No newline at end of file
diff --git a/Swap_Seat2.sql b/Swap_Seat2.sql
new file mode 100644
index 0000000..1e3face
--- /dev/null
+++ b/Swap_Seat2.sql
@@ -0,0 +1 @@
+SELECT S1.ID as id, COALESCE(S2.STUDENT,S1.STUDENT) AS student FROM SEAT S1 LEFT JOIN SEAT S2 ON (S1.ID + 1)^1 - 1 = S2. ID;
\ No newline at end of file
diff --git a/Tree.sql b/Tree.sql
new file mode 100644
index 0000000..4be0f76
--- /dev/null
+++ b/Tree.sql
@@ -0,0 +1,8 @@
+# Write your MySQL query statement below
+SELECT id, (
+    CASE
+    WHEN p_id is null then  'Root'
+    when id in (select p_id from tree) and id is not null then 'Inner'
+    else 'Leaf'
+END
+) AS type from tree;
\ No newline at end of file