Why in Ruby on Rails, when sorting, are numbers below 10 greater than those above 10?

Question

Ruby on Rails

For example, there are records in the database (MySQL), fields (num) with values ​​7, 31, 54.
So if I sort like this: Table.order('num DESC'), then this option will appear:
7
54
31
And vice versa (without DESC).
And if instead of 7 there will be 10 (and higher), then it will be in the normal order.
Why such a problem?

Answer 1

Because the num field seems to be character/text, and not one of the numeric types.