>
> > > > I'm just messign about with linq at the moment.
> > > >
> > > > I was wondering if there is a standard way to map between linq
> > > structures.
> > > >
> > > > i.e. I have a normalised database schema created in the
designer, I
> > > don't
> > > > want to bind to this directly but obviously to some slightly
> > > denormalisied
> > > > version of it.
> > >
> > > I don't see the 'obvious' part in that remark. For
FETCHING,
> it
> > > might be handy to have denormalized data in some areas, but for
saving
> entities,
> > > you definitely want to stick to the abstract entity definitions in
> your
> > > program's reality, not some denormalized pile of tables.
> >
> > UI usually operate on schema's that are derived and
> > denormalised...though I accept that in MS world this is less true.
>
> what does 'MS world' have to do with it?
>
Because different OO/RDB infrastructures encourage different approaches.
> If you denormalize data, that's in general only done for
> performance
> reasons. What you refer to isn't denormalizing data, it's creating new
> sets
> based on entity instances in the DB via projections on joined sets.
This
> data
> is by definition readonly.
Some of it will be readonly. (lets leave the denormalisation bit it
doesn't matter).
>
> > > Denormalization for performance purposes therefore isn't
> useful
> > > for entities. It's only useful for new sets, derived from the
entity
> > > instances, e.g. all orderid's with the customer's companyname
joined
> to
> it.
> >
> > Generally front end show all sorts of data that is derived or
> > denormalised from the underlying data, a simple grid map contain
several
> > joins, sometimes it makes sense to display those joins in separate
> > grids, often not.
>
> Though that's readonly data if it's presented in a single set.
You
> can
> create that easily with linq queries, that's the purpose of querying
on
> top of
> a normalized model:
>
> var q = from c in nw.Customers
> join orders o in nw.Orders on c.CustomerID equals
o.CustomerID
> select new { o.OrderID, c.CompanyName};
Correct....but this is a collection of anonymous types...it would be
much nicer if they were explicitly named....can you use named types in
the select clause?...I'll have a go.
>
> you then bind the q to a grid, done. You create new sets using
> projections. If
> you want to 'extend' entities to contain data from other entities,
you're
> IMHO
> not doing yourself a big favor, as the model is then in theory wrong,
plus
> you
> get problems when saving data.
>
As you say it will have to be readonly...this is fine.
> > > So take a look at indexed views. These are stored as-is and
therefore
> do
> > > offer performance optimizations. You then should be able to map an
> entity
> onto
> > > such a view. Just for fetching of course, Saving data should be
done
> with
> > > normal entities.
> > >
> >
> > Ok I'll take a look, but I'm not really interested in
performance...I
> > simple want to map a normalised collection of Linq data
> >
> > Customer & orders & location....to a denormalised/derived one
(Customer
> > extended to include derived orders and location) & orders......
>
> so you want to create a parallel hierarchy to customer-order-
> location?
Yes...and map from one to the other in a manner you describe, but
preferably using named types.
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