What is the relationship between mysql default and null?

RT, by the way, we can see that a blog has such a sentence. if there is a default value, it cannot be blank. Otherwise, there are conflicts, after the data is modified, it is still its default value. what I want to know is that if I set the default value and do not set the value to be null, the default value will be automatically filled in. if it is set to Null, what will happen...

RT
By the way, a blog has such a sentence.
If there is a default value, it is not allowed to be blank. Otherwise, there is a conflict between the two. after the data is modified, it is still its default value.
At the same time, I want to know if I set the default value and do not set the value to be null, will the default value be automatically filled in? what will happen if I set the value to null?
Of course, in my strict mode

Please come and save me

Reply content:

RT
By the way, a blog has such a sentence.
If there is a default value, it is not allowed to be blank. Otherwise, there is a conflict between the two. after the data is modified, it is still its default value.
At the same time, I want to know if I set the default value and do not set the value to be null, will the default value be automatically filled in? what will happen if I set the value to null?
Of course, in my strict mode

Please come and save me

If you don't want to, try it yourself. Some of them will know the answer after a try.