Namedquery using same table field multiple times with the use of a label

Question

Hi all,
i'm having some trouble with a namedquery. I'm trying to
use the following namedquery in Toplink to retrive some
data out of a database.
select proj.id
, proj.code
, proj.name
, proj.budget
, proj.status
, proj.startdate
, proj.enddate
, proj.mdr_id projleader_id
, med_leader.name projleader
, proj.mdr_id_valt_onder promanager_id
, med_promanager.name promanager
, proj.mdr_id_is_account_from accmanager_id
, med_accmanager.name accmanager
from uur_projecten proj
, uur_medewerkers med_leader
, uur_medewerkers med_promanager
, uur_medewerkers med_accmanager
where ( #p_name is not null or #p_search_string is not null )
and med_leader.id = proj.mdr_id
and ( proj.mdr_id = nvl( #p_name, proj.mdr_id )
or proj.mdr_id_valt_onder = nvl( #p_name, proj.mdr_id )
or proj.mdr_id_is_account_van = nvl( #p_name, proj.mdr_id ))
and (( #p_status is not null
and substr( proj.status, 1, 1 ) = upper( #p_status ))
or ( #p_status is null ))
and ( upper( proj.code ) like upper( '%' || #p_search_string || '%' )
or upper( proj.name ) like upper( '%' || #p_search_string || '%' ))
and med_promanager.id = proj.mdr_id_valt_onder
and med_accmanager.id = proj.mdr_id_is_account_van
order by decode( substr( proj.status, 1, 1 )
, 'A', 2, 'T', 3, 'F', 4, 1 ), proj.code desc
As you all can see the table ‘uur_medewerkers’ is been used trice to
determine the name for the corresponding ID. I have a Java class with
the fields for the results and created a Toplink descriptor to map
the fields to the database fields.
The problem is that for the 'projleader', 'promanager' and 'accmanager'
fields the results are null. The reason is probably that Toplink doesn't
recognize the fields because of the label for the tables.
Is there a way to make this work?
Greets, René

Answer 1

Post Author: quafto
CA Forum: .NET
Your query is not too clear so I'll do my best to answer it broadly.
You mentioned that you have a .NET web application where your users enter data on one screen and then may retrieve it on another. If the data is written in real time to a database then you can create a standard Crystal Report by adding multiple tables. The tables should be linked together using the primary and foreign keys in order to optimize the database query and give you a speedy report. Using unlinked tables is not recommended and requires the report engine to index the tables (it is quite slow).
You also mentioned you have a "PropID" to be used in a WHERE clause. This is a great place to use a parameter in your report. This parameter can then be used in your record selection formula inside Crystal Reports. The report engine will actually create the WHERE clause for you based on the parameter value. This is helpful because it allows you to simply concentrate on your code rather than keeping track of SQL queries.
Now, what Crystal does not do well with is uncertainty. When you design a report with X number of tables the report engine expects X number of tables to be available at processing time. You should not surprise the print engine with more or less tables because you could end up with processing errors or incorrect data. You may need to design multiple reports for specific circumstances.
Regarding the group expert question. I'm not sure how you would/could use the group expert to group a table? A table is a collection of fields and cannot be compared to another table without a complex algorithm. The group expert is used to group and sort records based on a field in the report. Have a look at the group expert section of the help file for more information.
Hopefully my comments have given you a few ideas.