Reports - Passing checkbox values and conditional column visibility

Question

Although I've been using Oracle databases for many years, I've to admit I'm rather new to APEX. I'm building a first prototype project to convince our project leaders and managers of the usefulness of the product for future projects (as for visual Database interfaces where the accent is on forms and reporting, it will often be faster and less expensive to build an APEX application instead of a full blown Java or C# webapp).
I'm however encountering some problems.
Let me start with a quick description. I've the following parent/child structures:
Provinces > Cities > Intersections > Loops > Loop Detections.
I basically want to make a report on the loop detections. Now, considering we'll have many thousands of detections a day, I made kind of a drilldown structure. You first choose your province, then the city, then the intersection and finally the loop. I didn't use lists to make the selection. Instead I made a (classic) report for each part as this allows me to give detailed information for each part. In each report, I made a link on the identifier. For example, when I select a province (by clicking on the link), I pass the province identifier to the cities report and use it in the query to limit my report to those cities for the given province. I repeat these step for the different parts, which in the end, gives me the loop detections for the selected loop. The good news is all this works fine. The person who'll be using this application however made a suggestion and asked if it would not be possible to select different loops and as such get the detections for several loops (the rest of the application stays the same). This however means I cannot use the column link anymore. Now, I was thinking in the direction of a checkbox. The column link is still there, but the user would also have the possibility to select several items in the report. I managad to add a checkbox to the report, linked to the loop identifier column. That's not exactly difficult. I cannot figure out however, how I can pass the selected identifiers to the next report (detections for the selected loops) and use it in the underlaying query of this report. The problem is, I don't know how to pass the checked values to the next page and how to use these values in the report query of that page. I suppose this must be possible, but I couldn't figure out how. I tried playing around with APEX_APPLICATION.G_Fxx and such. Remember I'm a newbie and this seems to fall under more advanced features.
I've uploaded images of the 2 concerning report pages for illustration:
http://img96.imageshack.us/img96/1497/apex01.jpg
http://img140.imageshack.us/img140/9868/apex02.jpg
A second point that's bothering me is the following. In the loop detection report I show a colum link (I picked an icon instead of the column value) for each row. I also have a column that shows the number of detections for the given loop (and day). Now, for some loops, there are no detections for that given day. As such, there's no point in selecting this loop, as the result will be an empty report. However, I still want to show the loop in the loop selection report, as it's still present (it's not as if it suddenly disappeared). Sure, no big problem and most users probably have sufficient intelligence to figure this out. However, it would be nice if I could make the icon (colum link) visible only for those loops that have detections, or in other words, for those records where number_of_detections (underlaying column COUNT) is greater than 0. I couldn't figure out a way to do this either. The Conditional Display option for a column didn't really offer me a solution here.
Before I forget, I'm using APEX 4.0.1 on an Oracle XE database.
Any tips or suggestions would be welcome! :)
Thanks.
Erwin

Answer 1

Hi,
You mean something like in this sample
https://apex.oracle.com/pls/otn/f?p=40323:55
You can store checked values to collection and use it then in another report where clause
See e.g. this post for how you can store checked rows to collection
Re: Need help with APEX_Collection
In sample DEPT report query is
SELECT
  CASE WHEN EXISTS(SELECT 1 FROM emp e WHERE e.deptno = d.deptno) THEN
    APEX_ITEM.CHECKBOX(1,c.c002,'onclick="saveDeptChk(this,'||c.seq_id||')"','true')
  END AS row_selector,
  c.c002 AS checked,
  d.DEPTNO,
  d.DNAME,
  d.LOC
FROM dept d,
  apex_collections c
WHERE c.collection_name = 'DEPT_CHK_COLLECTION'
  AND d.deptno = c.c001And EMP report
SELECT e.EMPNO,
  e.ENAME,
  e.JOB,
  e.MGR,
  e.HIREDATE,
  e.SAL,
  e.COMM,
  e.DEPTNO
FROM emp e,
  apex_collections c
WHERE c.collection_name = 'DEPT_CHK_COLLECTION'
  AND c.c002 = 'true'
  AND e.deptno = c.c001Regards,
Jari