RE: Useful Oracle books - C.J. Date theory vs. practicality

  • From: "Lex de Haan" <lex.de.haan@xxxxxxxxxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Sat, 29 May 2004 21:27:53 +0200

yes and no ... the ANSI/ISO SQL standard offers the three operators you
need:
"IS TRUE", "IS FALSE", and "IS UNKNOWN".
But as far as I know, no vendor has implemented these.
Note the power of these operators; they accept a Boolean argument.

The "IS NULL" becomes very clumsy as soon as multiple predicates are
involved.

One nice Oracle function (that has been around for quite a while, but was
undocumented until 10g)
is the LNNVL function. But again, it has many limitations.


SQL> select 'Bingo!' as result from dual
  2  where lnnvl(1=1);

no rows selected

SQL> c/1/2
  2* where lnnvl(2=1)
SQL> /

RESULT
------
Bingo!

SQL> c/=1/ is null/
  2* where lnnvl(2 is null)
SQL> /

RESULT
------
Bingo!

Kind regards,
Lex.

---------------------------------------------
visit my website at http://www.naturaljoin.nl
---------------------------------------------


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Nuno Souto
Sent: Saturday, May 29, 2004 16:58
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Useful Oracle books - C.J. Date theory vs. practicality

Always very hard to handle three-valued logic without some formal
construct or syntax that can cover all options.  Which brings me
to my next question, if you'd be so kind:

Is there an agreed syntax (or language) anywhere that can hold
against three-valued logic?  As in: commercially available?
Os is three-valued logic condemned to forever be the
fly in the ointment (so to speak) of SQL?
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