Comment on ADQL PR

[Tony Linde]

> Is the concept of variables and cursors of any use to ADQL ? 

Cursors across the VObs - now there's a challenge!

T.

> -----Original Message-----
> From: owner-voql at eso.org [mailto:owner-voql at eso.org] On 
> Behalf Of Francois Ochsenbein
> Sent: 08 June 2005 13:27
> To: voql at ivoa.net
> Subject: Re: Comment on ADQL PR 
> 
> 
> You are right Clive, the SQL92 standard effectively indicates 
> that the "into" clause represents a set of variables. The SQL 
> standardisation came only late, when it turned out that each 
> data-base vendor implemented his own SQL dialect... Postgres 
> accepts SELECT INTO TABLE table_name, MS-SQL and Sybase don't 
> need the "TABLE" keyword, Oracle accepts it as a "record" cursor... 
> 
> Is the concept of variables and cursors of any use to ADQL ? 
> 
> --Francois
> 
> >
> >On Mon, 6 Jun 2005, Francois Ochsenbein wrote:
> >
> >> Well, I'm surprised -- and doubt that Postgres really 
> represents THE 
> >> SQL standard ... SELECT INTO exists since the first 
> versions of SQL, 
> >> and does generates a table (or a relation if you prefer 
> the "purist"
> >> relational language)
> >
> >I hate to disagree with someone with as much experience as Francois, 
> >but my reading of the SQL1992 Standard (the latest one I can find 
> >online) is that SELECT INTO only refers to a [list of] 
> variables, not a 
> >table.  The syntax is pretty clear, but the semantics in the 
> Standard 
> >are pretty hard to understand, so my interpretation could be wrong.
> >
> >The PostgreSQL reference manual is quite helpful about 
> describing any 
> >differences between its syntax and that of Standard SQL.  It 
> has this 
> >to say about SELECT INTO:
> >
> ><quote>
> >SQL92 uses SELECT ... INTO to represent selecting values into scalar 
> >variables of a host program, rather than creating a new 
> table.  [snip] 
> >The PostgreSQL usage of SELECT INTO to represent table 
> creation is historical.
> >It is best to use CREATE TABLE AS for this purpose.
> ></quote>
> >
> >There is an excellent compilation of differences in the 
> implementation 
> >of SQL among popular DBMS at 
> http://troels.arvin.dk/db/rdbms/ although 
> >unfortunately it does not deal with this particular issue.  But the 
> >only conclusion that can be drawn from reading this 
> compilation is that 
> >the whole subject is a can of worms: *none* of the main DMBS vendors 
> >takes
> >*any* serious notice of *any* SQL Standards, so I don't see why our 
> >ADQL should be constrained by them.
> >
> >My suggestion is that we should continue to use SELECT INTO 
> <newtable> 
> >in the way that we originally planned, rather than have to get 
> >involvind in adding a whole new syntax tree for CREATE TABLE 
> AS, when 
> >we don't at present support anything like CREATE TABLE.
> >
> 
> ==============================================================
> ==================
> Francois Ochsenbein       ------       Observatoire 
> Astronomique de Strasbourg
>    11, rue de l'Universite F-67000 STRASBOURG       Phone: 
> +33-(0)390 24 24 29
> Email: francois at astro.u-strasbg.fr   (France)         Fax: 
> +33-(0)390 24 24 32
> ==============================================================
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>