ADQL v0.7.3

[Patrick Dowler]

On Wednesday 3 March 2004 13:49, Ray Plante wrote:
> As I've mentioned, my own reading of the SQL-92 standard suggests that
> ANDs and ORs are evaluated left-to-right in the absence of parentheses;
> however, I don't feel 100% on this.  The alternate interpretation would
> be
> that its system dependent.  Since we are developing ADQL for
> cross-database queries, I don't think this latter state is good one to
> be
> in.

It isn't specified because the db can optimise the query execution by chosing
the best of several logially equivalent evaluation orders. For services with a
database in the back-end, we definitely do not want to specify the order.

As for binary vs. 2..*, my recollection (logic book still in a box since last move :-)
is that logic ops are  - like the simple math ops - binary ops. This does not 
impact writing an expression on various logically equivalent ways, which is
how a db optimises query execution. 

-- 
Patrick Dowler
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