Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

"Marshall Spight" <marshall.spight_at_gmail.com> wrote in message news:1118119608.554172.320570_at_g49g2000cwa.googlegroups.com...

...[trim]...

> If SQL's NULL was really the absense of a value, then 1+NULL would
> be 1. (The sum of a series of numbers that is one long is that
> number.) Instead it is NULL, which is consistent with "value exists
> but is unknown" and inconsistent with "the absense of a value."

On the contrary, in TSQL (SQL Server) you can toggle between these two functionalities by using the following SET command:

SET CONCAT_NULL_YIELDS_NULL { ON | OFF } Remarks
When SET CONCAT_NULL_YIELDS_NULL is ON,
concatenating a null value with a string yields a NULL result. For example, SELECT 'abc' + NULL yields NULL. When SET CONCAT_NULL_YIELDS_NULL is OFF, concatenating a null value with a string yields the string itself (the null value is treated as an empty string). For example, SELECT 'abc' + NULL yields abc.

If not specified, the setting of the concat null yields null database option applies.

-- 
Pete Brown
IT Managers & Engineers
Falls Creek
Australia
www.mountainman.com.au