On Tue, 27 Aug 2002, Will K. wrote: > Date: Tue, 27 Aug 2002 01:09:32 +0000 > From: Will K. <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED] > Subject: NULL ? > > hello, > > Please dont tell me to RTFM on this one (cause I am already doing that), but > for clarity's sake... can someone tell me what it means when you use NULL > and NOT NULL in a query (specifically CREATE TABLE)? Also, when should I > use them? First, in database terms Null is different than an empty stirng or zero. It is closer to 'I do not know and it does not matter'. When you specify NULL in a table definition you are saying that the field you are defining in the table can take on a 'NULL' value. For this reason mysql does not allow fields which can be 'Null' to be part of an index. If you test a nullable field in a where clause you ask IS NULL or IS NOT NULL.
Hope this helps. > > Will K. > > > > _________________________________________________________________ > Send and receive Hotmail on your mobile device: http://mobile.msn.com > > > --------------------------------------------------------------------- > Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > > To request this thread, e-mail <[EMAIL PROTECTED]> > To unsubscribe, e-mail <[EMAIL PROTECTED]> > Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > Sincerely, William Mussatto, Senior Systems Engineer CyberStrategies, Inc ph. 909-920-9154 ext. 27 --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
