-1 and 0 for "Yes" and "No" (?)

Discussion in 'Access Table Design' started by croy, May 11, 2011.

  1. croy

    croy Guest

    It seems with MS Access that it is understood that -1
    corresponds with "Yes", and 0 corresponds with "No".

    Is that generally true for the database design community as
    a whole?
    croy, May 11, 2011
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  2. No. Not even Microsoft is consistant; in SQL/Server a Boolean field is stored
    as a Bit, with +1 being TRUE and 0 being FALSE.

    I think it's safe now to assert that 0 is FALSE and nonzero is TRUE, but do
    read the documentation carefully!

    John W. Vinson [MVP]
    Microsoft's replacements for these newsgroups:
    and see also http://www.utteraccess.com
    John W. Vinson, May 11, 2011
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  3. If you program on that assumption, your code will be very
    cross-compatible with all databases, seems to me. True is really
    nothing more than NOT FALSE.
    David-W-Fenton, May 12, 2011
  4. It is a dangerous assumption. NOT can be a bitwise operator on
    integers. In two's-complement arithmetic, NOT 1 equals -2, and both
    are considered true by the non-zero is true assumption.

    If this is a concern, use a boolean type. If you can not do
    that, then determine true and false using something like
    false=not true
    and then use those variable where you need boolean values.


    Gene Wirchenko
    Gene Wirchenko, May 18, 2011
  5. But it's not in VBA, which is what you'd be using in Access.

    Of course, it's certainly true that you could be using it in SQL, as
    well, but if you're not writing passthroughs, it will be executed by
    Jet/ACE, so results will be reliable.
    I don't think any of this is relevant to any circumstances in which
    one would be using Access as one's development platform.

    That WAS what we were talking about, no?
    David-W-Fenton, May 21, 2011
  6. On 21 May 2011 19:37:22 GMT, "David-W-Fenton"

    No. OP asked "Is that generally true for the database design
    community as a whole?"


    Gene Wirchenko
    Gene Wirchenko, Jun 21, 2011
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