MySQL Order by multiple fields

Is the result of adding only one sort:

As you can see, a single field is no problem. What if I join C2? It's c2.

It can be found that the order here is first ordered by C1, and then for the C1 after the same sequence of the same elements, and according to C2 do a descending sort. The following are the C1,C2, the results are consistent.

As a summary, each field is separated by a comma when multiple fields are ordered, and is added by default if the field does not indicate the sort method. The sort is sorted first by first field, if you have the same followed by subsequent fields.

MySQL Order by multiple fields