'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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