On Wed, 15 Jan 2003, Matthew Nuzum wrote:
> Well, this is somewhat of a follow up to my previous post regarding self
> joins. Now what I'm hoping to do is "virtually" combine the results
> from two different record sets into one apparent record set.
Fortunately we have the set functions, specifically UNION ALL in this
case.
> Here is the skeleton of my application's data structure. There is a
> table called "folders" and a table called "files".
>
> They look like:
> | files | folders
> ============= ============
> x| fileid x| folderid
> | filename | foldername
> | folderid | parentid
> | dsply_order | dsply_order
>
> files.folderid is fk to folders.folderid, folders.parentid is field for
> self joining to folderid.
>
> As a side note, I'd probably need to add a field that would indicate 1
> if the file came from files otherwise count(folders.*) WHERE parentid =
> folderid so that I can see if the folder is empty.
>
> As another side note, this operation will be performed quite frequently
> and should be fast.
>
> As I think about it, it seems that the only logical way would be to do
> this at the application level, not inside postgres. Please correct me
> if I'm wrong.
Maybe something like (minus the number of files/empty part):
CREATE VIEW viewname ASSELECT fileid, filename, folderid, dsply_order FROM files UNION ALLSELECT folderid, foldername,
parentid,dsply_order FROM folders;
SELECT * from viewname where folderid=23 order by dsply_order;
Depending on whether you want a count of files or just an empty
or not, and whether you want info on whether a particular entry
is a file or folder, you'll probably need to add to the above.
