Re: lost on self joins

On Wed, Jan 15, 2003 at 03:19:38PM -0500, Matthew Nuzum wrote:
> > -----Original Message-----
> > From: Tomasz Myrta [mailto:jasiek@klaster.net]
> > Sent: Wednesday, January 15, 2003 3:00 PM
> > To: Matthew Nuzum
> > Cc: pgsql-sql@postgresql.org
> > Subject: Re: [SQL] lost on self joins
> > >Finaly, a table to allow a many to many join called files_folders
> > > | files_folders
> > >================
> > >x| ffid
> > > | folderid (fk to folders.folderid)
> > > | fileid (fk to files.fileid)
> > 
> > Strange. Do you need this table? Can one file exist in several
> > directories?
> > If not, you can just add "folderid" field into table files.
> 
> Good point.  No, it can't exist in multiple folders, so I guess it's
> overkill to do a many to many here.  Thanks for the moment of clarity.

Unless you're attempting to accurately map Unix filesystem sematics, where
the exact same file _can_ be in more than one place in the filesystem
(hard links).  It's all about the inode. One of the wierder bits of unix
that you don't often see used in common occurances.

Ross