"MySQL" not NULL default 0

1.SQL not NULL constraint

The NOT NULL constraint enforces that the column does not accept null values.

A NOT NULL constraint forces a field to always contain a value. This means that if you do not add a value to the field, you cannot insert a new record or update the record.

The following SQL statement enforces that the "id_p" column and the "LastName" column do not accept NULL values:

NOT NULLNOT NULL, FirstName varchar (255), Address varchar (255), City varchar (255))


2.default 0 means the default value is 0
If the field is set to not NULL, there is a default value to fill when no value is entered ~

"MySQL" not NULL default 0