englandr@phoenix.Princeton.EDU (Scott Louis Englander) (07/24/89)
Does commercial database software generally have a way to represent
missing numbers? I'm using Fox on the Mac, and the best i can do is use
a value (-99) that is unlikely to appear naturally in the data. This is
problematic for fields that are, say, one character logical fields, etc.
I really do need to distinguish between 0 and missing, or false and
missing.
Other Mac software (e.g. Igor {scientific plotting}, compilers) uses the
special value NaN (Not a Number) for this purpose; it seems like it
would be simple enough to incorporate it in a program like FoxBASE.
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- Scottbrianc@daedalus (Brian Colfer) (07/26/89)
In article <9571@phoenix.Princeton.EDU> englandr@phoenix.Princeton.EDU (Scott Louis Englander) writes: >Does commercial database software generally have a way to represent >missing numbers? I'm using Fox on the Mac, and the best i can do is use >a value (-99) that is unlikely to appear naturally in the data. This is >problematic for fields that are, say, one character logical fields, etc. >I really do need to distinguish between 0 and missing, or false and >missing. > >Other Mac software (e.g. Igor {scientific plotting}, compilers) uses the >special value NaN (Not a Number) for this purpose; it seems like it >would be simple enough to incorporate it in a program like FoxBASE. Well most relational systems use SQL and use a value of NULL to mean no data. C.J.Date doesn't like this and E.F. Codd thinks there should be 3 valued logic to account for this... no easy solution to this problem. The real difficulty is in how do you treat NULL when doing agregate operations on the data... is it considered when calulating averages etc. And how do you treat dates etc. oooo its a problem... One solution is to let this No Data value be configurable for every column in table... ============================================================================= Brian | UC San Francisco | E-mail: USENET, Internet, BITNET Colfer | Dept. of Lab. Medicine |...!{ucbvax,uunet}!daedalus.ucsf.edu!brianc | S.F. CA, 94143-0134 USA | brianc@daedalus.ucsf.edu | PH. (415) 476-2325 | BRIANC@UCSFCCA.BITNET ----------------------------------------------------------------------------- "Leave your body and soul at the door ..." -- Oingo Boingo =============================================================================