Added Consecutive Numbers

Author: ignacio-chiazzo

LeetcodeProblems/Databases/Consecutive_Numbers.sql

@@ -0,0 +1,33 @@
+/*
+Consecutive Numbers
+https://leetcode.com/problems/consecutive-numbers/
+
+Write a SQL query to find all numbers that appear at least three times consecutively.
+
++----+-----+
+| Id | Num |
++----+-----+
+| 1  |  1  |
+| 2  |  1  |
+| 3  |  1  |
+| 4  |  2  |
+| 5  |  1  |
+| 6  |  2  |
+| 7  |  2  |
++----+-----+
+For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.
+
++-----------------+
+| ConsecutiveNums |
++-----------------+
+| 1               |
++-----------------+
+*/
+
+SELECT DISTINCT(l1.Num) AS ConsecutiveNums
+FROM
+    Logs l1, Logs l2, Logs l3
+WHERE (
+       l1.Num = l2.Num AND l1.Id = (l2.Id + 1) AND
+       l2.Num = l3.Num AND l2.Id = (l3.Id + 1)
+)

README.md

@@ -81,6 +81,7 @@ To run a specific problem in your console, go to the file test, add the call to
 ### Databases
 | Problems | Level | Link |
 |-|-|-|
+| [Consecutive Numbers](/LeetcodeProblems/Databases/Consecutive_Numbers.sql) | Medium | https://leetcode.com/problems/consecutive-numbers |
 | [Department Highest Salary](/LeetcodeProblems/Databases/Department_Highest_Salary.sql) | Medium | https://leetcode.com/problems/department-highest-salary |
 | [Exchange Seats](/LeetcodeProblems/Databases/Exchange_Seats.sql) | Medium | https://leetcode.com/problems/exchange-seats |
 | [Nth Highest Salary](/LeetcodeProblems/Databases/nth_Highest_Salary.sql) | Medium | https://leetcode.com/problems/nth-highest-salary |