How to make a selection sorted by two fields in mysql?

Question

MySQL

there is a table

col1 | col2
     |
null | 2
1    | null
null | 4
3    | null
null | 6
5    | null

you need to somehow select by two fields, so that it would turn out: 1,2,3,4,5,6
if you execute SELECT * FROM table ORDER BY col1, col2, then the selection is 2,4,6,1,3,5, that is, sorted by each of these fields separately

Answer 1

SELECT COALESCE(col1,col2) as someName
ORDER BY someName
UPD: Just take your time and figure out how the COALESCE function works. If you have both fields null or both have a value, you may need different results and a different approach.