'AS' - ADQL WD v1.05

Noel Winstanley Noel.Winstanley at manchester.ac.uk
Tue Jul 4 06:39:05 PDT 2006

On 4 Jul 2006, at 09:29, Yuji SHIRASAKI wrote:

> From: Noel Winstanley <Noel.Winstanley at manchester.ac.uk>
> Subject: 'AS' - ADQL WD v1.05
> Date: Tue, 4 Jul 2006 01:04:06 +0200
>> I notice that alhough table aliases are required, it is optional
>> whether the 'AS' keyword is used to denote this. I'd argue that
>> having optional syntax doesn't help implementors, and is just
>> confusing to users. Furthermore, I don't think the statement on  
>> page 4
>> "ADQL/s and ADQL/x are translatable to each other without loss of
>> information"
> Since the 'AS' keyword does not have any information, this statement
> is true even if the 'AS' keyword is dropped out between the  
> translations.

the same can be argued for comments - there's no information there  
that alters the semantics of the query.
however, if a query adql/s is to be converted to adql/x and then back  
to adql/s, if we've decided that preserving comments is desirable  
then I'd say usage of optional syntax is equally important to  
preserve - otherwise the user will be presented with a query that

> 'AS' keyword is just introudced for compatibility with the standard  
> SQL.

and why is compatability with standard SQL important for adql/s ? I  
hope we're not suggesting that AS would be required for some  
databases, but not for others.

> The rolse of the 'AS' keyword is just to clearly seprate the table  
> name
> and alias name. There is no semantic role for this. Allowing to use
> the 'AS' keyword is just for convinience for an SQL master.

ok. so if it's convenient and clearly separtates the table and alias  
names, why don't we use it all the time. I'm not objecting to the  
'AS' keyword - just that it's optional.

> Yuji Shirasaki.
>> is possible, considering optional syntax, unless the adql/x version
>> has a way of recording which optional fragments of syntax have been
>> used (and I really hope this isn't the case).
>> so I'd say choose one, either one, but don't include both.
>> same applies to column aliases too.
>> ---
>> http://wiki.astrogrid.org/bin/view/Main/NoelWinstanley
>> Senior Java Developer, AstroGrid Project
>> Jodrell Bank Observatory, University of Manchester

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