sql1 complete

README.md

@@ -1,5 +1,43 @@
 # Sql1
 
 1. Problem 1: Big Countries (https://leetcode.com/problems/big-countries/)
+
+    --Solution
+
+    SELECT  name,
+            population,
+            area
+    FROM world
+    WHERE area >= 3000000
+    OR population >= 25000000;
+
 2. Problem 2: Nth Highest Salary (https://leetcode.com/problems/nth-highest-salary/)
+
+    --Solution
+
+    CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
+    BEGIN
+    RETURN (
+        # Write your MySQL query statement below.
+            SELECT  DISTINCT IFNULL(salary,null)
+            FROM (SELECT    salary,
+                            DENSE_RANK() OVER(ORDER BY salary DESC) AS rnk
+                FROM employee
+                ) a
+            WHERE rnk = N
+        );
+    END
+
 3. Problem 3: Delete Duplicate Emails (https://leetcode.com/problems/delete-duplicate-emails/)
+
+    --Solution
+
+    DELETE FROM person
+    WHERE id NOT IN  
+        (SELECT DISTINCT id FROM
+            (SELECT id,
+                    email,
+                    ROW_NUMBER() OVER(PARTITION BY email ORDER BY id) rwn
+            FROM person) a
+        WHERE rwn = 1
+        );