Re: [Zope-dev] dupe column names not supported (Shared.DC.ZRDB) ?
The semantics of Zope's database functionality is such that duplicate column names are not (and probably never will be) possible in the same result set. This is because Zope expects to access columns by name rather than position. Therefore each one must have a distinct name. The only workaround I can see would be some sort of automatic renaming of columns, but that sounds like a bad idea since it introduces some serious bug potential if the columns are renamed differently then the application expects. Just for curiousity, what is the use case for returning multiple columns with the same name? Sounds dubious to me. -Casey On Tuesday 17 December 2002 02:11 pm, Ross J. Reedstrom wrote: Same problem has been reported with Oracle 8.1, since it too will return duplicate names. The SQL92 spec is a bit ambiguous about whether all returned column names must be unique. Ross On Tue, Dec 17, 2002 at 01:09:13PM -0500, Adam Manock wrote: specifically with: SELECT W1.city, W1.temp_lo AS low, W1.temp_hi AS high, W2.city, W2.temp_lo AS low, W2.temp_hi AS high FROM weather W1, weather W2 WHERE W1.temp_lo W2.temp_lo AND W1.temp_hi W2.temp_hi; Error, exceptions.ValueError: Duplicate column name, city Traceback (innermost last): Module ZPublisher.Publish, line 98, in publish Module ZPublisher.mapply, line 88, in mapply Module ZPublisher.Publish, line 39, in call_object Module Shared.DC.ZRDB.Connection, line 115, in manage_test Module Shared.DC.ZRDB.Results, line 52, in __init__ ValueError: Duplicate column name, city ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] dupe column names not supported (Shared.DC.ZRDB) ?
On Tue, Dec 17, 2002 at 02:25:27PM -0500, Casey Duncan wrote: The semantics of Zope's database functionality is such that duplicate column names are not (and probably never will be) possible in the same result set. This is because Zope expects to access columns by name rather than position. Therefore each one must have a distinct name. Oh, I understand the problem: just reporting that PostgreSQL isn't the only one doing it. The only workaround I can see would be some sort of automatic renaming of columns, but that sounds like a bad idea since it introduces some serious bug potential if the columns are renamed differently then the application expects. Yeah, that'd suck. Just for curiousity, what is the use case for returning multiple columns with the same name? Sounds dubious to me. I'm not aware of a use case, per se. It comes about from implementing this bit of the SQL92 standard: 7.9.9.b) If the i-th derived column in the select list does not specify an as clause and the value expression of that derived column is a single column reference, then the column name of the i-th column of the result is C. Note that that says 'C', not 'CR'. i.e. is _must_ be the undecorated column name, not the column reference (schema.table.column) The next subclause (7.9.9.c) handles the case of it not being a single column reference (like a function, or somthing), and says it's then 'implementation dependent' and only needs to be unique in the set of tables referenced by the SQL. It's not clear whether that's supposed to include the 'derived table' that is the output of this 'query specification'. Ross -- Ross Reedstrom, Ph.D. [EMAIL PROTECTED] Research Scientist phone: 713-348-6166 The Connexions Project http://cnx./rice.edu fax: 713-348-6182 Rice University MS-39 Houston, TX 77005 ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] dupe column names not supported (Shared.DC.ZRDB) ?
Just for curiousity, what is the use case for returning multiple columns with the same name? Sounds dubious to me. A self join will return multiple columns with the same name unless AS keyword is used. The use of AS keyword is supposed to be optional. Assuming that a user does use AS, labeling of the returned columns will be at the discretion of the user, and therefore again not guaranteed to be unique. I would guess that if Zope assumes that column names are unique, changing that assumption now would be a major p.i.t.a. :-) Adam ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
