Re: XQuery

Michael Rys wrote:

>Just a nitpick: SQL WHERE clauses fail with a conversion error if a
>conversion fails and the query processor executes a plan that leads to
>the execution of the offending conversion.
>
>Actually, the current XQuery rules are pretty close to SQL's rules in
>that respect.
>  
>
Wow, I've been away from SQL too long, I had forgotten this.   I had a 
dim memory that SQL is also non-deterministic; you might cause/avoid 
hitting an exception, for example, by creating an index on a certain column.

Well, if XQuery is working like SQL then at least it's something that's 
been proven by experience.

Basically, it seems like
  - a (non-null) column value in a relational table (accessed via SQL) 
corresponds to a sequence in an XML document (accessed via XQuery)  (ie, 
a list of values rather than just a single value)
  - a NULL value in a relational table (accessed via SQL) corresponds to 
an empty sequence. (ie, a list of no values)

Other than that SQL and XQuery are "the same", so to speak.

Bill

Received on Thursday, 16 October 2003 22:41:30 UTC