Hi Daniel, there is one subtle difference between COBOL (cum suis) and SQL, with regards to leaving fields empty. COBOL doesn't have three-valued logic. 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! and another "regardless" statement: regardless how far you are off-base, it always makes sense to stay close to a bottle of Scotch... Cheers, Lex. --------------------------------------------- visit my website at http://www.naturaljoin.nl --------------------------------------------- -----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Daniel Fink Sent: Friday, May 28, 2004 19:35 To: oracle-l@xxxxxxxxxxxxx Subject: Re: Useful Oracle books - C.J. Date theory vs. practicality Ah, nulls... One system I worked on had several columns with the following COLUMN_A VARCHAR2(15) NOT NULL w/Check constraint value in (<list of values>, 'NULL') ARGH! I think one of the issues is that many (perhaps most) people do not understand the implementation of NULL in Oracle. The above example is just one of several common 'beliefs' that I have seen. I wonder how much this has to do with the tendency (at least what I perceive) to think of 2-valued logic when it comes to TRUE/FALSE and to avoid ambiguity. "Is the sun shining?" "Of course it is" (when I am sitting in an office where I cannot see out a window). The 'correct' answer is "I don't know, let's go to a window and check.", but that seems somewhat ridiculous to actually say in a conversation.
BEGIN:VCARD VERSION:2.1 N:de Haan;Lex FN:Lex de Haan ORG:Natural Join B.V. TEL;WORK;VOICE:+31.30.2515022 TEL;HOME;VOICE:+31.30.2518795 TEL;CELL;VOICE:+31.62.2955714 TEL;WORK;FAX:+31.30.2523366 ADR;WORK:;;Pieter Breughelstraat 10;Utrecht;;3583 SK;Netherlands LABEL;WORK;ENCODING=QUOTED-PRINTABLE:Pieter Breughelstraat 10=0D=0AUtrecht 3583 SK=0D=0ANetherlands URL;WORK:http://www.naturaljoin.nl EMAIL;PREF;INTERNET:lex.de.haan@xxxxxxxxxxxxxx REV:20040224T160439Z END:VCARD