Re: NULLs: theoretical problems?
Date: Sat, 11 Aug 2007 11:38:20 -0700
>> The ANSI standard defines NULL as follows:
"null value: A special value that is used to indicate the absence of any data value." <<
We needed to word it that for reasons of implementation. In Codd's model there is only one NULL, a type-less marker. But hardware has to allocate storage and therefore we had to allow for "CAST (NULL AS <data type>)" to signal the SQL compiler about that column's storage. There are some situations where the compiler cannot determine the data type of a CASE expression without explicit CAST() help.
Does anyone seriously gripe about floating point numbers having gaps in them because of implementation considerations? No, we just pick on poor little NULL ... Received on Sat Aug 11 2007 - 20:38:20 CEST