diff --git a/problem1.sql b/problem1.sql
new file mode 100644
index 0000000..7674c98
--- /dev/null
+++ b/problem1.sql
@@ -0,0 +1,5 @@
+-- Write your PostgreSQL query statement below
+SELECT name, population, area
+FROM World
+WHERE area >= 3000000
+OR population >= 25000000;
\ No newline at end of file
diff --git a/problem2.sql b/problem2.sql
new file mode 100644
index 0000000..1317646
--- /dev/null
+++ b/problem2.sql
@@ -0,0 +1,14 @@
+CREATE OR REPLACE FUNCTION NthHighestSalary(N INT) RETURNS TABLE (Salary INT) AS $$
+BEGIN
+  RETURN QUERY (
+    -- Write your PostgreSQL query statement below.
+    WITH CTE AS (
+        SELECT e.salary, DENSE_RANK() OVER(ORDER BY e.salary DESC) AS rnk
+        FROM Employee e
+    )
+    SELECT DISTINCT c.salary
+    FROM CTE c
+    WHERE c.rnk = N
+  );
+END;
+$$ LANGUAGE plpgsql;
\ No newline at end of file
diff --git a/problem3.sql b/problem3.sql
new file mode 100644
index 0000000..86a6898
--- /dev/null
+++ b/problem3.sql
@@ -0,0 +1,5 @@
+-- Write your PostgreSQL query statement below
+DELETE FROM Person
+USING Person p2
+WHERE Person.email = p2.email
+AND Person.id > p2.id;