Well, I know I'm gonna catch flak for this, but oh well, here goes anyway I send an off list mail to Alain to ask for some more specific information about what he is trying to do so that we can find a way to do it.
But this I will say to the whole list... What is the point of setting up a referential integrity constraint just to exploit it in the way Alain described? Given what the manual says about the limitations of these type of constraints (at least so far) seems to me that it is not desirable to use them. While I know that NULL is by definition a part of every column (just like in set theory math where you have the null set is a subset of every set), NULL is not rendered as an actual entry in any column when looking at the output of any select * or similar SQL statement. Clearly NULL is both there and not there at the same time, and it depends greatly on context which understanding is used for any given command. >From a very practical standpoint, I think that the output Alain described is >desirable in over 90% of implementation ideas (and 100% desirable in all of my >previous implementations) Standards be what Standards be, but standards can be either changed or ignored, depending on if it benefits one to do so. This is especially true when dealing with NULL, heck, some databases don't even support the NULL concept at all Rance Hall 308.238.2455 Internal Office Extensions: 2455 or 6655 PC Programmer, The Buckle, Inc. [EMAIL PROTECTED] -----Original Message----- From: Christopher Thompson [mailto:[EMAIL PROTECTED]] Sent: Tuesday, April 09, 2002 12:05 PM To: Alain Del Giust; [EMAIL PROTECTED] Subject: Re: mySQL and innoDB On Tuesday 09 April 2002 11:07 am, Alain Del Giust wrote: > "if you have a foreign key constraint, that field must be one of the values > of the referenced column and that column, being an index, is never NULL" > > OK so my understanding is that it is impossible with mySQL to do such > things wich are basic with at least: > Oracle > Sybase Adaptive Server Enterprise > Sybase Adaptive Server Anywhere What are you saying? If you are saying these databases allow a primary key column (or a unique key column) to contain a NULL, they are violating SQL92. By extension, any column that is a foreign key can also not be NULL. Perhaps you are saying something else. But if you are saying this, you can hardly take MySQL to task for properly supporting SQL92 (at least, in this instance). --------------------------------------------------------------------- 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 --------------------------------------------------------------------- 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
