HP Intelligent Management Center Standard Software Platform - Manual (Page 673)

SQL database considerations
Since indexes are not critical with SQL data, the primary concern with both
linked tables and subreports is whether or not there is a selection formula in
the primary report that puts range limits on Table A. See
Linking data files .
Linked SQL tables
If there are range limit conditions in the selection formula, the program passes
those conditions down to the server.
• If there is a selection formula that puts range limits on Table A, the server
locates the records in Table A that satisfy the selection criteria (2),
matches them up with the appropriate records in Table B (100), and
returns 200 merged records to the Report Engine.
• If there is no selection formula, or if there is a selection formula that does
not put range limits on Table A, the server matches up each record in
Table A (26) with the appropriate records in Table B (100), and returns
2600 merged records to the Report Engine.
In either case, the Report Engine will then apply the entire selection formula
to the merged records.
Subreports and SQL databases
If you are creating a primary report based on Table A and a subreport based
on Table B:
• The number of subreports that are run is determined by the selection
formula situation in the primary report:
• If there is a selection formula and it passes down range limits on Table
A, the program runs a subreport only for those records that satisfy
range limit conditions (2).
• If there is no selection formula, or if the selection formula does not
pass down range limits on Table A, the program runs a subreport for
every record in Table A (26).
Crystal Reports 2008 SP3 User's Guide 673
25 Understanding Databases
Linking tables