| From: | Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at> |
|---|---|
| To: | "'Joe Conway'" <joseph(dot)conway(at)home(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | AW: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. S tand ards |
| Date: | 2001-06-19 07:10:25 |
| Message-ID: | 11C1E6749A55D411A9670001FA687963368333@sdexcsrv1.f000.d0188.sd.spardat.at |
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| Lists: | pgsql-hackers |
> -- If I have interpreted SQL92 correctly UNKNOWN IS TRUE should return
> FALSE, and UNKNOWN IS NOT TRUE is equivalent to NOT (UNKNOWN IS TRUE) ==>
> TRUE. Is this correct?
No, I do not think it is valid to say "should return true|false"
I think they should return UNKNOWN. Only when it comes to evaluating the
"... WHERE UNKNOWN;" can you translate it to "... WHERE FALSE;", or in the
output function.
My interpretation would be:
UNKNOWN IS TRUE --> FALSE
UNKNOWN IS NOT TRUE --> FALSE
NOT (UNKNOWN IS TRUE) --> FALSE
Andreas
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