Re: VARCHAR2: NULL value vs. empty string

Comments in-line

VC wrote:

> Hello Daniel,
>
> Frank is actually right that Oracle is _not_ SQL'92 or SQL'99 compliant
> with respect to empty strings treatment.
>
> 1. In SQL'92 an empty string is _not_ null. Oracle have neglected to fix
> this problem for close to eleven years.

Provide a reference to either SQL standard that supports what you said.

Because I've been involved with this for a long time, corresponded with Joe Celko, and there is nothing about your statement that I believe to be true.

Before you respond you might want to look at this:

http://developer.mimer.com/validator/comparison/upd_comparison_chart.tml

And this from Stanford University:

http://www-cs-students.stanford.edu/~wlam/compsci/sqlnulls

Note the statement: "A boolean comparison between two values involving a NULL returns neither true nor false, but unknown in SQL's three-valued logic"

This is not possible with null strings because '' does indeed equal ''.

Also note the reference '[3]' to that statement:

C. J. Date and Hugh Darwen A Guide to the SQL Standard. Fourth edition, Addison-Wesley, Reading, Massachusetts, 1997. (ISBN 0-201-96426-0) page 239.

If you can find a better person to discuss relational theory and the ANSI standard than C. J. Date I'd like to know who it is.

Oracle has not admitted something that isn't true ... and it just isn't true. I'd suggest you stop believing everything you read from Microsoft Press.

-- 
Daniel Morgan
http://www.outreach.washington.edu/ext/certificates/oad/oad_crs.asp
http://www.outreach.washington.edu/ext/certificates/aoa/aoa_crs.asp
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