Two dimensional Grouping

Question

Hi 2 all,
I'm trying to build a report starting from two complex PL/SQL query like this(simplified):
SELECT SUM(x),SUM(y),SUM(z),Name,type,product
FROM DESC A, STORE1 B, STORE2 C, store3 D, store4 E
WHERE b.ID=c.ID(+)
AND b.ID=d.ID(+)
AND b.ID=e.ID(+)
AND a.code=b.code
AND a.product='oneproduct'(...another query with !='oneproduct')
group by b.Name,b.type
I need to have on each report page the results of the two queries grouped by type, one page for each (Name).
how can I have the content of Name field on the header/margin (as a title) and the remainder data below grouped by the same Name?
=> In the end I should have one page for each Name
thanks
Matteo

Answer 1

On the other hand I do recall having read somewhere
that the "new" operator
is very costly and should strictly be
avoided in loops.Not that expensive performance-wise. It could potentially suck up a lot of memory if you are creating LOTS of objects
Now for the concrete case of reading some user's
datasets from a database
and then processing them further, is it advisable
to instantiate a new user object for each row, or
where is the alternative
to be found?I think you should create an object to represent each row.
two dimensional collections (any favourites in java)I always create my own. I try to use Vectors and Hashtables exclusively, depending on my needs re: ordering and lookup. Mixing and matching these could result in Vectors of Hashtables, Vectors of Vectors, Hashtables of Vectors, and Hashtables of Hashtables.
synchronized one dimensional collections each
representing one field in a
table ? (is this really more performant than simple
classes)Doubtful - any gain that you get by avoiding the constructor call would be obviated by the overhead of iterating through multiple lists and keeping them synchronized.
a Collection of Collections (here comes the new
operator again)Same as two-dimensional collections.
I remember having seen inner classes used for the
purpose of holding just a
couple of attributes, is there some performance
advantage like "the class
loader does not have to look for the class".No advantage - the only reason to create an inner class is to prevent other classes from using those objects. The inner class still compiles to a separate class object that needs to be loaded separately.