Re: Implementing a pivot table / cross table
Re: Implementing a pivot table / cross table
- Subject: Re: Implementing a pivot table / cross table
- From: "Jerry W. Walker" <email@hidden>
- Date: Fri, 17 Mar 2006 10:07:56 -0500
Hi, Lachlan,
On Mar 17, 2006, at 7:32 AM, Lachlan Deck wrote:
Hi there,
On 17/03/2006, at 10:19 PM, Jerry W. Walker wrote:
I've never implemented a cross table in WO (or in any other
environment, for that matter), but if, by cross table, you mean a
table used to statistically derive information about the
relationships between the row and column elements, then I question
doing it in WO at all.
Awe come on Jerry, stick with the programme: 'anything you can do
WO can do better' ;-)
Darn, Lachlan, I try, I really do try... :-)
You must have missed the part where I said that I've never
implemented a cross table. So I didn't do it and won't ask WO to. ;-)
If it's a statistical cross table, then the focus is on a table
which is easily implemented in an relational database.
Hmm. Just thinking out loud... I'd suppose, as with any problem
domain, that the focus is on the ultimate 'view' of the data. That
view we happen to call an Object. An Object (in theory) is
oblivious to where the data comes from that it receives.
I think Rico's problem domain is that of a statistical table, which
fits quite conveniently into an rdb table. Given that the problem
domain thinks of the data in a cross table as a "table of data", and
that there are very convenient tools out there for working with the
data in that form, I think that WO would tend more to get in the way
than to help in this particular case (he says as a lover of NEARLY
all things WO).
For more insight into this problem domain, check here:
http://www.roselladb.com/cross-table.htm
So I think that Jean-François's message was probably a good deal more
helpful to Rico than mine.
Regards,
Jerry
So, the simple/default view (for most WO Apps) correlates to a
single row from a single table. i.e., an EOEnterpriseObject with
properties and relationships as defined in a corresponding EOEntity
instance. The info on the attributes and relationships are relevant
to the view.
So, let's say we want a Cross-join (the Cartesian product of the
compared tables) that's akin to:
SELECT * FROM Actor CROSS JOIN Movie
The derived view will contain rows consisting of all columns from
Actor followed by all columns from Movie. That should mean that at
the point you know of the tables (err woops, I mean Entities) that
are to be involved in the cross-join (and in what order) you now
have the information necessary to dynamically build an EOEntity
with the corresponding attributes. All that's needed is
yourEOEntity,setExternalQuery("SELECT t0.name, etc....FROM Actor
t0, Moview t1");
But, at some point (when the database grows) you'll need to be able
to cull the list of results. Perhaps raw rows would be a better
approach...
with regards,
--
Lachlan Deck
--
__ Jerry W. Walker,
WebObjects Developer/Instructor for High Performance Industrial
Strength Internet Enabled Systems
email@hidden
203 278-4085 office
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