Done SQL1

SQL1.sql

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+# Problem 1: Big Countries (https://leetcode.com/problems/big-countries/)
+# Write your MySQL query statement below
+SELECT name, population, area
+FROM World
+WHERE area >= 3000000 OR population >= 25000000;
+
+# Problem 2: Nth Highest Salary (https://leetcode.com/problems/nth-highest-salary/)
+# Write your MySQL query statement below
+CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
+BEGIN
+  RETURN (
+       # Write your MySQL query statement below.
+        WITH TEMP AS
+        (
+            SELECT id, salary, DENSE_RANK() OVER(ORDER BY salary DESC) AS ranks
+            FROM Employee
+        )
+        SELECT IFNULL(salary, null)
+        FROM TEMP
+        WHERE ranks = N
+  );
+END
+
+# Problem 3: Delete Duplicate Emails (https://leetcode.com/problems/delete-duplicate-emails/)
+# Write your MySQL query statement below
+DELETE p2
+FROM Person p1
+JOIN Person p2
+ON p1.email = p2.email AND p2.id > p1.id