Create 619-biggest_single_number.sql

Author: milangrahovac

619-biggest_single_number.sql

@@ -0,0 +1,83 @@
+-- 619. Biggest Single Number
+
+-- Table: MyNumbers
+
+-- +-------------+------+
+-- | Column Name | Type |
+-- +-------------+------+
+-- | num         | int  |
+-- +-------------+------+
+
+-- This table may contain duplicates (In other words, there is no primary key for this table in SQL).
+-- Each row of this table contains an integer.
+ 
+
+-- A single number is a number that appeared only once in the MyNumbers table.
+-- Find the largest single number. If there is no single number, report null.
+-- The result format is in the following example.
+
+ 
+
+-- Example 1:
+
+-- Input: 
+-- MyNumbers table:
+
+-- +-----+
+-- | num |
+-- +-----+
+-- | 8   |
+-- | 8   |
+-- | 3   |
+-- | 3   |
+-- | 1   |
+-- | 4   |
+-- | 5   |
+-- | 6   |
+-- +-----+
+
+-- Output: 
+-- +-----+
+-- | num |
+-- +-----+
+-- | 6   |
+-- +-----+
+
+-- Explanation: The single numbers are 1, 4, 5, and 6.
+-- Since 6 is the largest single number, we return it.
+-- Example 2:
+
+-- Input: 
+-- MyNumbers table:
+-- +-----+
+-- | num |
+-- +-----+
+-- | 8   |
+-- | 8   |
+-- | 7   |
+-- | 7   |
+-- | 3   |
+-- | 3   |
+-- | 3   |
+-- +-----+
+
+-- Output: 
+-- +------+
+-- | num  |
+-- +------+
+-- | null |
+-- +------+
+
+-- Explanation: There are no single numbers in the input table so we return null.
+
+
+SELECT
+    MAX(unique_nums.num) AS num
+FROM
+    (
+        SELECT num
+        FROM MyNumbers
+        GROUP BY num
+        HAVING COUNT(num) = 1
+    ) AS unique_nums
+;