Tom Lane wrote:
> Bruce Momjian <br...@momjian.us> writes:
> > Tom Lane wrote:
> >> Bruce Momjian <br...@momjian.us> writes:
> >>> + Exclusion constraints ensure that if any two rows are compared on
> >>> + the specified columns or expressions using the specified operators,
> >>> + at least one of these operator comparisons will be false. The
> >>> syntax is:
> >>
> >> Isn't that phrasing outright incorrect? Consider nulls.
>
> > Well, doesn't a comparison returning null really behave as false?
> > Should I reword it as "not true" or "false or null"?
>
> Either one.
I used "false or null".
--
Bruce Momjian <br...@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
Index: doc/src/sgml/ddl.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/ddl.sgml,v
retrieving revision 1.91
diff -c -c -r1.91 ddl.sgml
*** doc/src/sgml/ddl.sgml 1 Apr 2010 01:18:17 -0000 1.91
--- doc/src/sgml/ddl.sgml 6 Apr 2010 02:13:57 -0000
***************
*** 861,867 ****
<para>
Exclusion constraints ensure that if any two rows are compared on
the specified columns or expressions using the specified operators,
! at least one of these operator comparisons will be false. The syntax is:
<programlisting>
CREATE TABLE circles (
c circle,
--- 861,868 ----
<para>
Exclusion constraints ensure that if any two rows are compared on
the specified columns or expressions using the specified operators,
! at least one of these operator comparisons will return false or null.
! The syntax is:
<programlisting>
CREATE TABLE circles (
c circle,
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