Biggest Single Number

Problem

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.

Solution

The problem Biggest Single Number can be solved using keywords GROUP BY and HAVING along with the function MAX.

Implementation

# Write your MySQL query statement below

SELECT MAX(num) AS num
FROM
  (
    SELECT num
    FROM mynumbers
    GROUP BY num
    HAVING COUNT(num) = 1
  ) AS T;