Re: Updateable views...

Gavin Sherry <swm@linuxworld.com.au> writes:
> I haven't had time to look into it further, but it occurs to me that
> handling views which rely on joins would be far from trivial.

Views containing joins would not be updatable; problem solved.  The set
of views the automatic-rule-generation machinery needs to handle are
those defined as updatable by the SQL spec.  SQL92 says
        12)A <query specification> QS is updatable if and only if the fol-           lowing conditions hold:
           a) QS does not specify DISTINCT.
           b) Every <value expression> contained in the <select list> imme-             diately contained in QS
consistsof a <column reference>, and             no <column reference> appears more than once.
 
           c) The <from clause> immediately contained in the <table ex-             pression> immediately contained in
QSspecifies exactly one             <table reference> and that <table reference> refers either to             a base
tableor to an updatable derived table.
 
             Note: updatable derived table is defined in Subclause 6.3,             "<table reference>".
           d) If the <table expression> immediately contained in QS imme-             diately contains a <where clause>
WC,then no leaf generally             underlying table of QS shall be a generally underlying table             of any
<queryexpression> contained in WC.
 
           e) The <table expression> immediately contained in QS does not             include a <group by clause> or a
<havingclause>.
 

The reference to 6.3 appears to be pointing at this:
        8) A <derived table> is an updatable derived table if and only if           the <query expression> simply
containedin the <subquery> of the           <table subquery> of the <derived table> is updatable.
 

I haven't quite wrapped my head around what clause 12d means, but 12c is
perfectly clear that you only get one table reference.
        regards, tom lane