Re: lost on self joins
От | Tomasz Myrta |
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Тема | Re: lost on self joins |
Дата | |
Msg-id | 3E25F6F0.6030501@klaster.net обсуждение исходный текст |
Ответ на | Re: lost on self joins (Tomasz Myrta <jasiek@klaster.net>) |
Список | pgsql-sql |
Ross J. Reedstrom wrote: >>>>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 If we are talking about Unix filesystems - this solution doesn't let you change filename when using hard (symbolic) links. Anyway I wish I could use symbolic link on windows machine the same like on linux one... I think more important for Matthew would be protection against circular join which causes query to hang up. Tomasz
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