Query executes too often

rbuser

I have a problem with a subreport inside a detail band. The data query is
re-run for every instance of the subreport even though its parameters are
set once at the beginning of the main report.

The report and its subreports share several common DataPipelines and I admit
to using the data from wherever it is available in the report hierarchy.

What can cause the detail band to trigger a 'master' query ?

Regards,
Sigurd

nicocizik

Hi Sigurd,

When creating a master/detail report it is best to have complete separation
betweent the master dataset and the detail dataset. See the article below.

------------------------------------------------
TECH TIP: Fundamentals of Report Data Traversal
------------------------------------------------


1. Single Table Listing Report

Assign the Report.DataPipeline property and leave the
DetailBand.Pipeline unassigned.

The report will traverse the data from start to end (based on the
datapipeline range settings and honoring any filters you've placed on
the datset etc.)


2. Master/Detail Report:

A. Assign the Report.DataPipeline property to the master. Create a
subreport in the detail band and assign the childreport.DataPipeline to
the detail datapipeline.

Use either the visual linking features available from the Report
Designer's Data tab, or Use standard Delphi dataset linking to define
the relationships between the datasets.

The Report will traverse the master records and for each, the subreport
will traverse the detail data related to the master.


3. Master with 2 Details

Configure as in 2 above. Add an additional subreport to the detailband.
Set subreport.ShiftRelativeTo property to the point to the first
subreport. Connect the ChildReport's DataPipeline to the detail data.


4. Report connected to no datapipelines.

When Report.AutoStop is set to True, the Report will print a single
detail band.

When Report.AutoStop is set to False, the Report will print detail bands
until instructed
to stop. You can control when the report stops by setting the
Report.PageLimit property or by calling Report.DataTraversalCompleted
method. Otherwise the report will never stop.


Additional Notes:
----------------

1. SubReports have a Report property that is of type TppChildReport.
Thus, programmatically you can code SubReport.Report.DataPipeline :=
myDataPipeline.

2. ChildReport's traverse data following the same rules as above. A
ChildReport prints in its entirety each time it gets a turn to print.

3. For a Child style SubReport use the Title/Summary band rather than
the Header/Footer (or use a GroupHeader/GroupFooter combo). A standard
Header/Footer will not work because these always print at the very
top/bottom of the page.

4. Do not filter the dataset of modify it any way once the report.Print
command is issued. If you need to do master/detail and cannot use
linked datasets, then use the master DataPipeline.OnRecordPositionChange
event to filter the detail dataset.

5. The reports and datapipelines use dataset bookmarking. Make sure
the dataset can support bi-directional navigation.



Check out the RBuilder\Demos\Reports\Demo.dpr project. Reports 0071,
0072, 0073 show examples of master w/mutliple detail style reports.
Number 0072 has two detail reports.


--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

Consider two tables:

Table1
id | tekst
1 abc
2 xyz
3 nop

Table2
id | amount
1 12.4
1 9.4
1 .7
2 234
2 12
3 7.3

when table1 is master and table2 is detail and report is set up
according to tip given below, is there executed three "SELECT Amount
FROM Table2 WHERE Id = :Id" or one "SELECT Id, Amount FROM Table2 ORDER
BY Id" ?
I guess the first is what is done, second solution would be preferred.
(eg. first table have 1 000 000 records, second have 10 000)

rbuser

To answer my own question

Check out tech-tips 120 in group Data access to learn how to control
this behaviour.

nicocizik

Sorry Frode,

Somehow your initial message did not show up in my newsreader. Glad you
got it worked out.

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com