Subject Re: [Firebird-devel] [ firebird-Bugs-451953 ] Indexes with NULLs
Author Dmitry Kuzmenko
Hello, Sean!

"Leyne, Sean" wrote:

> What was meant by this items?

> > Allow for NULL values to be included in the index
> > data, using the syntax CREATE [WITHNULLS] INDEX...

At last I've reviewed Gruber's "SQL Instant Reference",
and found that UNIQUE constraints ALLOW NULLs.
Primary Key constraint, of course, does not allow NULLs.
That is the difference.
And, UNIQUE does not need NOT NULL field constraint.

As Gruber states, this corresponds to ANSI SQL92 Entry Level.
So I think IB/FB does not conform to ANSI SQL92 UNIQUE
constraint definition...

Sorry I can't give page numbers where I've found this,
I'm reading russian translation.

Dmitry Kuzmenko, Epsylon Technologies.
TechSupport Manager. InterBase support.
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(095) 530-28-06.