SQL - Creating a table with two timestamp column with no default value
===

I want to create a table with two column, one "created" and one "modified", with a timestamp type, but I don't want them to have a default value. But when I create them, it automaticly puts CURRENT_TIMESTAMP as default for at least one of them, and also on update, 

How can I just have type timestamp with no default or on update value for any of my column?

Thanks