diff --git a/Rankemails.sql b/Rankemails.sql
new file mode 100644
index 0000000..e239967
--- /dev/null
+++ b/Rankemails.sql
@@ -0,0 +1,26 @@
+# Write your MySQL query statement below
+# -------------------------- Using Window Function DENSE_RANK()--------------
+-- SELECT 
+--     Score,
+--     DENSE_RANK() OVER (ORDER BY Score DESC) AS 'rank'
+-- FROM 
+--     Scores;
+
+# ------------------------- Handling Null with Null as rank 1 -----------------
+SELECT 
+    Score,
+    DENSE_RANK() OVER (ORDER BY COALESCE(Score, 1) DESC) AS 'RANK'
+FROM 
+    Scores;
+
+# ------------------------- Using subquery-------------------------------
+-- SELECT 
+--     Score,
+--     (SELECT COUNT(DISTINCT Score)
+--     FROM scores s2
+--     WHERE s2.score >= s1.score
+--     ) AS 'rank'
+-- FROM
+--     Scores s1
+-- ORDER BY
+--     score DESC;
diff --git a/Top3Dept.sql b/Top3Dept.sql
new file mode 100644
index 0000000..13a3b59
--- /dev/null
+++ b/Top3Dept.sql
@@ -0,0 +1,15 @@
+WITH RankedSalaries AS (
+    SELECT 
+        d.name AS Department,
+        e.name AS Employee,
+        e.salary AS Salary,
+        DENSE_RANK() OVER (PARTITION BY e.departmentId ORDER BY e.salary DESC) AS salary_rank
+    FROM Employee e
+    JOIN Department d ON e.departmentId = d.id
+)
+SELECT 
+    Department,
+    Employee,
+    Salary
+FROM RankedSalaries
+WHERE salary_rank <= 3;
diff --git a/TreeNode.sql b/TreeNode.sql
new file mode 100644
index 0000000..a68ca6d
--- /dev/null
+++ b/TreeNode.sql
@@ -0,0 +1,32 @@
+# Write your MySQL query statement below
+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;
\ No newline at end of file
diff --git a/exchangeSeats.sql b/exchangeSeats.sql
new file mode 100644
index 0000000..28bdb4e
--- /dev/null
+++ b/exchangeSeats.sql
@@ -0,0 +1,22 @@
+# Write your MySQL query statement below
+#-------------------Using ODD/EVEN ---------------
+-- SELECT(
+--     CASE 
+--         WHEN mod(id, 2) != 0 AND id != cnt THEN id + 1
+--         WHEN mod(id, 2) != 0 AND id = cnt THEN id
+--         ELSE id - 1
+--     END) AS id, student 
+--     FROM 
+--         Seat, (SELECT COUNT(*) AS cnt FROM Seat) as count_table
+--     ORDER BY id 
+#---------------- Using LEFT JOIN and XOR function------------------
+SELECT 
+    s1.id, COALESCE(s2.student, s1.student) AS 'student'
+FROM
+    Seat s1 
+    LEFT JOIN
+    Seat s2
+    ON
+    (s1.id + 1) ^ 1 - 1 = s2.id
+ORDER BY
+    s1.id
\ No newline at end of file