PU Biggest Single Number

Table number contains many numbers in column num including duplicated ones.
Can you write a SQL query to find the biggest number, which only appears once.

+---+
|num|
+---+
| 8 |
| 8 |
| 3 |
| 3 |
| 1 |
| 4 |
| 5 |
| 6 | 

For the sample data above, your query should return the following result:

+---+
|num|
+---+
| 6 |

Note:
* If there is no such number, just output null.

Solution:

# Write your MySQL query statement below
SELECT max(num) as num
FROM 
    (
    SELECT num
    FROM number
    GROUP BY num
    HAVING count(num) = 1
    ) AS tmp

Summary:

• Nothing to say.

LeetCode: 619. Biggest Single Number