NULL vs NOT NULL [closed]

Question

In sql database column, empty fields will be set to NULL unless we specify it using NOT NULL. What are the advantages of using one instead of the other? Thanks!

Answer 1

If you need to represent unknown data in a column, you make it nullable. If you will always have data in the column, it's better to make it not nullable, as

1. Dealing with nulls can be annoying and counterintuitive
2. It saves a bit of space
3. On some database systems, null values are not indexed.

Answer 2

When a field is set to NOT NULL, it cannot be empty. Which means you have to specify a value for that field when inserting a record.