how to use sub-sequence

Tablenumbercontains many numbers in columnnumincluding 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

Approach: UsingsubqueryandMAX()function [Accepted]

Algorithm

Use subquery to select all the numbers appearing just one time.

Then choose the biggest one usingMAX().

select num

from number

GROUP BY num

having count(num) = 1

select MAX(num) as num

from (

select num

from number

GROUP BY num

having count(num) = 1

)