Completed SQL1

BigCountries

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+SELECT name, population, area FROM World
+WHERE area >=3000000 OR population >= 25000000

Problem2_NthHighestSalary.Sql

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+CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
+BEGIN
+  RETURN (
+      # Write your MySQL query statement below.
+WITH CTE AS(
+    SELECT *, DENSE_RANK() OVER (Order By Salary desc) AS Rnk FROM Employee
+    )
+
+    SELECT DISTINCT IFNULL(salary, null) FROM CTE
+    WHERE Rnk = N
+
+  );
+END

Problem3_DeleteDuplicateEmails.sql

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+# Write your MySQL query statement below
+DELETE FROM Person
+WHERE id IN(
+    SELECT id FROM
+    (SELECT *, ROW_NUMBER() OVER(PARTITION BY email ORDER BY id) AS Instances FROM Person )p
+    WHERE p.Instances>1)