Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!drn.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.icl.net!newsfeed.fjserv.net!nx02.iad01.newshosting.com!newshosting.com!68.1.17.232.MISMATCH!peer01.cox.net!cox.net!cyclone1.gnilink.net!spamkiller2.gnilink.net!gnilink.net!trndny01.POSTED!9244eeff!not-for-mail From: "David Cressey" Newsgroups: comp.databases.theory References: <1133747821.754959.79980@g43g2000cwa.googlegroups.com> <1133835469.329650.234930@g14g2000cwa.googlegroups.com> <0o5cp1haj0743335l14u86krdhiojd2e5k@4ax.com> <1133920747.354768.173010@z14g2000cwz.googlegroups.com> <36dhp1dv7d9r2r2ujp4qeor3cnunbsmp8m@4ax.com> Subject: Re: 3vl 2vl and NULL Lines: 25 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Message-ID: Date: Mon, 12 Dec 2005 04:16:22 GMT NNTP-Posting-Host: 71.127.4.210 X-Complaints-To: abuse@verizon.net X-Trace: trndny01 1134360982 71.127.4.210 (Sun, 11 Dec 2005 23:16:22 EST) NNTP-Posting-Date: Sun, 11 Dec 2005 23:16:22 EST Xref: dp-news.maxwell.syr.edu comp.databases.theory:35060 "Hugo Kornelis" wrote in message news:aaepp1l4g1h3ud0imb120471k08g9rdaf0@4ax.com... > All true. The DB engine can conclude the datatype of the NULL from the > datatype of the column that holds the NULL. Or when used as a literal in > a query (though I fail to see why anyone would do that), it can either > choose a datatype from the context or choose a default datatype and use > implicit conversion rules to get at the destination datatype. I would change the wording slightly. The DB engine can conclude the datatype a value would have if it were in the place currently occupied by the NULL. NULL doesn't have a datatype. The place marked by a NULL can contain a value drawn from a domain. Any value in that lpace has a datatype. NULL doesn't.