NOT NULL

IGNORE NULL ??

This is an integrity constraint that allows the database table creator to prevent columns containing a null value.
Typically a null value represents a missing data item
To deny null values you can create a table with a NOT NULL constraint on a column.

Applying On Creation

CREATE TABLE MyProducts 
( 
ProductID INTEGER 
Price MONEY NOT NULL - is column cannot contain NULL 
Description CHAR(40) NULL - this column can contain NULL 
) 

Applying After Creation

You must always specify the column type and size
If the size is omitted then the default maximum size is applied.

ALTER TABLE MyProducts 
ALTER COLUMN Price MONEY NOT NULL 

You cannot add this constraint to a column that already contains null values