RE: Useful Oracle books - C.J. Date theory vs. practicality
- From: "Lex de Haan" <lex.de.haan@xxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 28 May 2004 21:43:04 +0200
Hi Jared,
the difference becomes apparent if you try a condition like the following:
'Mort Subite' = NULL
This condition is neither TRUE nor FALSE; it evaluates to UNKNOWN.
According to three-valued logic, NOT UNKNOWN evaluates to UNKNOWN;
therefore, both statements will execute their ELSE branch;
so the first one executes statement 2, and the second one executes statement
1.
My math teacher (many moons ago) usually would say at this point: QED.
Kind regards,
Lex.
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visit my website at http://www.naturaljoin.nl
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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Jared.Still@xxxxxxxxxxx
Sent: Friday, May 28, 2004 20:24
To: oracle-l@xxxxxxxxxxxxx
Subject: RE: Useful Oracle books - C.J. Date theory vs. practicality
> just for fun, check out these two commands:
>
> IF (some condition) THEN (statement 1) ELSE (statement 2);
> IF NOT (some condition) THEN (statement 2) ELSE (statement 1);
>
> regardless the contents of your data structures,
> in COBOL these two are equivalent but in PL/SQL they are not!
You've really lost me here.
12:22:41 rsysdevdb.radisys.com - jkstill@dv01 SQL>
12:22:46 rsysdevdb.radisys.com - jkstill@dv01 SQL> l
1 begin
2
3 if true then
4 dbms_output.put_line('TRUE');
5 else
6 dbms_output.put_line('FALSE');
7 end if;
8
9 if not true then
10 dbms_output.put_line('FALSE');
11 else
12 dbms_output.put_line('TRUE');
13 end if;
14
15* end;
12:22:47 rsysdevdb.radisys.com - jkstill@dv01 SQL> /
TRUE
TRUE
PL/SQL procedure successfully completed.
Maybe I need a slug of Ardberg to understand.
Jared
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