diff --git a/01-BigCountries.sql b/01-BigCountries.sql
new file mode 100644
index 0000000..127e2d3
--- /dev/null
+++ b/01-BigCountries.sql
@@ -0,0 +1,4 @@
+-- Problem 1: Big Countries (https://leetcode.com/problems/big-countries/)
+select name, population, area 
+from world
+where area >= 3000000 or population >=25000000
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diff --git a/02-NthHighestSalary.sql b/02-NthHighestSalary.sql
new file mode 100644
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--- /dev/null
+++ b/02-NthHighestSalary.sql
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+-- Problem 2: Nth Highest Salary (https://leetcode.com/problems/nth-highest-salary/)
+
+CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
+BEGIN
+RETURN (
+    # Write your MySQL query statement below.
+    with cte as (
+        select salary, dense_rank()
+        over (order by salary desc) as rnk
+        from employee
+    )
+    select distinct ifnull(salary, null)
+    from cte
+    where rnk=N
+  );
+END
\ No newline at end of file
diff --git a/03-DeleteDuplicateEmails.sql b/03-DeleteDuplicateEmails.sql
new file mode 100644
index 0000000..e2ec28b
--- /dev/null
+++ b/03-DeleteDuplicateEmails.sql
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+-- Problem 3: Delete Duplicate Emails (https://leetcode.com/problems/delete-duplicate-emails/)
+
+delete p1 from person p1
+cross join person p2
+where p1.email = p2.email and p1.id > p2.id
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