NOT NULL ensures that a field cannot be left blank. This is necessary for primary keys because a null value would lead to a collapse in relationships. For other fields, NOT NULL is used to speed SELECT queries and again to make sure the field is filled.
Think of the many cases in which you would not want a field left blank: a customer's last name or zip code, a product's name or id number, a payment amount. Were any of those fields allowed to be NULL, the system of which they are a part could fall on its face. We wouldn't want that, would we? Edward Dudlik Becoming Digital www.becomingdigital.com ----- Original Message ----- From: "Jonas Geiregat" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, 16 June, 2003 11:02 Subject: NOT NULL ? I really don't get the user of NOT NULL anyone knows a good page on the manual that talks about it I can't seem to locate one. Or any good resource help to help me figure this out would be greate regards -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
