[Ur] dml DELETE and SELECT, way of referring to rows

[Adam Chlipala]

Daniel Patterson wrote:
> Code that is written like:
>
>          dml (DELETE FROM s
>               WHERE Session = {[v.Session]} );
>
> with table defined as:
> table s : {LoggedIn : time, User : string, Session : string}
>    PRIMARY KEY LoggedIn
>
> and v being the a cookie value with attribute Session
>
> Works, where as:
>
>          dml (DELETE FROM s
>               WHERE s.Session = {[v.Session]} );
>
> Does not.
>
> This is different from how the Sql example worked (where DELETE was used
> with t.A), but the same as how the Tree example works.
>    

I'm not trying to implement any SQL standard exactly.  The table being 
DELETEd from is always called T.  This is easier to implement with type 
inference, etc..

The signature of the Basis module defines it all rigorously.