When talking about expressions,views, or any other construct that could combine values from multiple tables I think it is reasonable to provide null as the table name. Any one or any process requesting the table name has to understand that not all SQL parameters have a base table name. However, in the case where a single table is involved, table and schema names should be available.
Reggie > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:pgsql-hackers- > [EMAIL PROTECTED]] On Behalf Of Tom Lane > Sent: Sunday, January 26, 2003 7:39 PM > To: Dave Cramer > Cc: PostgreSQL Hackers Mailing List > Subject: Re: [HACKERS] Request for qualified column names > > Dave Cramer <[EMAIL PROTECTED]> writes: > > So for a "select a, b, a+b as sum from c" returns c.a, c.b, ?table?.sum > > This might be something to consider as part of the planned protocol > overhaul. We cannot simply change the returned column names --- at > least not without breaking a lot of application code. But if we > return table name (and schema name too!) as separate fields of the > 'T' message, and make them accessible through new PQfoo accessor > functions, then no existing applications would break. > > But there are more than a few definitional issues to be settled before > you'll convince me this idea is fully baked. Some things that come to > mind immediately: > > What happens with views? Given > create view v as select col as vcol from tab; > select vcol from v; > are you expecting to get back "v.vcol"? Or "tab.col"? > > What happens with FROM-clause aliases? Supposing tab really has a > column "col", what do you expect to see from > select * from tab AS a(t1), tab AS b(t2) WHERE ... > You could make a case for either "tab.col, tab.col" or "a.t1, b.t2" > (in the latter case, you can't realistically return a schema name). > But you will probably break existing code if you do the former, since > currently the output columns are labeled t1, t2. > > What happens with join aliases (similar issues to above)? > > Do you think > select col as foo from tab > should return "tab.foo", or just "foo"? I'd lean to the latter; > "tab.foo" seems awfully misleading. Or maybe you're wanting it > to ignore the AS and return "tab.col"? Don't think that will fly. > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
