Is it necessary to add NOT NULL to a column, if there are certainly no NULLs there?

Question

MySQL

Will it give anything in terms of performance or just avoid errors?

Answer 1

1. Null means no value. If you have a column that, logically, cannot be without a value, but null can be written into it, this is evidence of the poor design of your
database . On small volumes, you will not notice this, but if you work with a large, highly loaded base, speed will play a huge role

Answer 2

It will help you avoid mistakes.