RE: Sanity check re. layering of views
- From: david wendelken <davewendelken@xxxxxxxxxxxxx>
- To: ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 16 Mar 2005 07:41:00 -0800 (PST)
>Do you think it's reasonable to see five layers of views?
>My instinct it would be ideal to have at most three layers of views.
That's not a bad instinct! I used two views to turn a database where each
field in a "logical record from the user's viewpoint" is stored in a separate
database record, and in which there are multiple versions of answers for each
field (only one of which is "the latest") into a view that showed the "logical
record" as if it were a table, and only showed the latest version of each
field. Could have been done in one, with the first view as a query in the
from clause, but it was easier to debug in two pieces and to write the code
generators to build the views the way I did it. There were thousands of
"logical record types" and a code generator was the only way to do it.
Not knowing the precise problem to be solved, I can't say "5 is more than you
need". 5 might be the number needed to make it maintainable by the team of sql
developers that you have. :)
>I don't think it's reasonable to create any layers of views. It's cheaper
>and easier to create a brand new view. Cheaper in that when the query goes
>bad, it's easier to debug and manage. And Easier speaks for itself.
Actually, I tend to think of the layers of views as subroutines in a program.
Sometimes it makes more sense to just skip the subroutines and write it all in
one big glop, other times it makes sense to separate out specific tasks to be
done in subroutines. It's a matter of balancing speed, complexity, time, and
re-useability.
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