This only covers the syntax of the SQL language. I have not read the standard
in detail, but I am sure that somewhere it says that it is up to the relational
database engine HOW it evaluates the SQL and that it is allowed to transform
the quireies.
Quoting Jonathan Gennick <jonathan@(protected) >:
> Thursday, July 15, 2004, 10:06:04 AM, Wolfgang Breitling
> (breitliw@(protected)) wrote:
>
> Ok. I 've started to do a bit of digging in the 1999 ANSI SQL
> standard. Section 7.5 describes the FROM clause as
> containing a <table reference list >:
>
> FROM <table reference list >
>
> <table reference list > ::= <table reference > ...
>
> Later, section 7.6 defines <table reference > as follows:
>
> <table reference > ::= <table primary > | <joined table >
>
> <table primary > can be many things, one of which is a
> <derived table >, and a <derived table >, in turn, is defined
> as a <table subquery >.
>
> The standard does seem here, to put a subquery in the FROM
> clause on an equal footing with a table that you specify by
> name. A subquery is simply another way of specifying a
> table.
>
--
Regards
Wolfgang Breitling
Oracle 7,8,8i,9i OCP DBA
Centrex Consulting Corporation
www.centrexcc.com
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