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 "Real" copy of Codd's 12 (13) Rules for RDBMS Rate Topic Display Mode Topic Options
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 Posted Monday, August 16, 2010 7:46 PM
 SSC-Forever Group: General Forum Members Last Login: Yesterday @ 10:52 PM Points: 42,083, Visits: 39,479
 mtillman-921105 (8/16/2010)I was a philosophy major (and a psychology major by the way), so I started reading my book on elemetary logic about empty sets over the weekend. Now here is the clencher - it said that an empty set was represented by a zero. I won't argue that an "empty set" is represented by a zero but that has nothing to do with NULL's in a database.Again, you should have just stopped where you were because that's all that matters about NULL's in a DB. --Jeff Moden"RBAR is pronounced "ree-bar" and is a "Modenism" for "Row-By-Agonizing-Row".First step towards the paradigm shift of writing Set Based code: Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column." Helpful Links:How to post code problemsHow to post performance problems
Post #970107
 Posted Tuesday, August 17, 2010 2:16 AM
 Forum Newbie Group: General Forum Members Last Login: Tuesday, September 23, 2014 8:06 AM Points: 1, Visits: 83
Post #970184
 Posted Tuesday, August 17, 2010 5:32 AM
 SSCrazy Eights Group: General Forum Members Last Login: Yesterday @ 2:03 PM Points: 9,836, Visits: 11,913
 mtillman-921105 (8/16/2010)I was a philosophy major (and a psychology major by the way), so I started reading my book on elemetary logic about empty sets over the weekend. Now here is the clencher - it said that an empty set was represented by a zero. Did the book really say "a zero", or did you mistake the Greek letter phi (φ or Φ) - which is the usual symbol used to denote the empty set - for a 0? Or do you have it upside down, did it actually say "in standard set theory the empty set is used to denote the (ordinal) number zero"? It's quite possible that you are quoting correctly and your elementary logic did say something quite bizarre, but in my experience the most common reason for someone to claim that the empty set is represented by 0 is one of those two misunderstandings. Mistaking Φ for 0 is particularly common amongst those who grew up with batch computoing, since there was a fairly common convention that on coding sheets phi should be used for zero and theta for letter "O" in order to disambiguate them for the girls who typed from the coding sheets, whether to produce punched cards, or paper tape, or for direct data entry to the computer; perhaps your book was written - or proof-edited - by someone from that generation. Tom
Post #970269
 Posted Tuesday, August 17, 2010 6:22 AM
 Ten Centuries Group: General Forum Members Last Login: Friday, January 30, 2015 8:42 AM Points: 1,332, Visits: 19,324
 Tom.Thomson (8/17/2010)mtillman-921105 (8/16/2010)I was a philosophy major (and a psychology major by the way), so I started reading my book on elemetary logic about empty sets over the weekend. Now here is the clencher - it said that an empty set was represented by a zero. Did the book really say "a zero", or did you mistake the Greek letter phi (φ or Φ) - which is the usual symbol used to denote the empty set - for a 0? Or do you have it upside down, did it actually say "in standard set theory the empty set is used to denote the (ordinal) number zero"? It's quite possible that you are quoting correctly and your elementary logic did say something quite bizarre, but in my experience the most common reason for someone to claim that the empty set is represented by 0 is one of those two misunderstandings. Mistaking Φ for 0 is particularly common amongst those who grew up with batch computoing, since there was a fairly common convention that on coding sheets phi should be used for zero and theta for letter "O" in order to disambiguate them for the girls who typed from the coding sheets, whether to produce punched cards, or paper tape, or for direct data entry to the computer; perhaps your book was written - or proof-edited - by someone from that generation.I never made that connection, that's why people slash their zeroes....huh, learn something new every day... ---------------------------------------------------------How best to post your questionHow to post performance problemsTally Table:What it is and how it replaces a loop"stewsterl 80804 (10/16/2009)I guess when you stop and try to understand the solution provided you not only learn, but save yourself some headaches when you need to make any slight changes."
Post #970322
 Posted Tuesday, August 17, 2010 8:13 AM
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Post #970434
 Posted Tuesday, August 17, 2010 9:11 AM
 SSChasing Mays Group: General Forum Members Last Login: Friday, January 22, 2016 2:15 PM Points: 600, Visits: 3,852
 Jeff Moden (8/17/2010)Alain Rastoul (8/17/2010)Hi Jeff,Here you'll find 3 papers from E.F.Codd ,A Relational Model of Data for Large Shared Data Bankshttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.98.5286&rep=rep1&type=pdfExtending the Database Relational Model to Capture More Meaninghttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.84.9469&rep=rep1&type=pdfRELATIONAL COMPLETENESS OF DATA BASE SUBLANGUAGEShttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.86.9277&rep=rep1&type=pdfHTHAlainFinally! Someone get's back to the original subject of my poor ol' hijacked thread! Thanks, Alain. I'll take a look.You're right Jeff. I can take a hint, so I started a new thread on NULLs. http://www.sqlservercentral.com/Forums/Topic970493-374-1.aspx ______________________________________________________________________The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge. - Stephen Hawking
Post #970496
 Posted Tuesday, August 17, 2010 1:35 PM
 SSC-Forever Group: General Forum Members Last Login: Yesterday @ 10:52 PM Points: 42,083, Visits: 39,479