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The Implications of the Bug More | Login | Reply

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Not quite right (Score:1)

by huxtonr (8912)

Now consider a simpler, yet silly, example: SELECT first_name FROM employee WHERE salary > 50000; What happens if the salary field is NULL? You'll get a list of employees whose known salary is NULL.

I can't figure out what you meant to say there, but the query doesn't seem to go with the text.
In this scenario, it is the case that everyone has a salary; you just don't know what some of them are. So here's the kicker: SELECT first_name FROM employee WHERE salary = salary; Th
- Re:Not quite right (Score:2)
  
  by Ovid (2709) on 2009.12.08 1:51 (#71345) Homepage Journal
  
  Ack, fixed the typo regard "known salary is null".
  You don't know that though. Not within the terms of the database. If you did, they'd have a numeric salary and not NULL.
  That's entirely the point. Database "logic", when combined with NULLs, returns answers that we really know are not true. I don't mean "within the terms of the database". p = p is true, regardless of whether or not a poorly designed query language says otherwise.
  
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