check duplicate mysql row

Question

I have a mysql table that contains field_one, field_two, field_three

I want to check if field_one contains a duplicate value (like if it was unique).

How to do that in mysql?

Thanks

Answer 1

This will show you values for field_one that occur more than once:

select field_one, count(*) as Count
from MyTable
group by field_one
having count(*) > 1