Setting Column Names in Dynamic Pivot Query

Question

Hi all,
I'm having trouble setting column names in a dynamic pivot query and was wondering if someone could please help me figure out what I need to do.
To help you help me, I've setup an example scenario in my hosted account. Here's the login info for my hosted site at [http://apex.oracle.com]
Workspace: MYHOSTACCT
Username : DEVUSER1
Password : MYDEVACCTAnd, here is my test application info:
ID     : 42804
Name   : dynamic query test
Page   : 1
Table 1: PROJECT_LIST         (Alias = PL...  Listing of Projects)
Table 2: FISCAL_YEAR          (Alias = FY...  Lookup table for Fiscal Years)
Table 3: PROJECT_FY           (Alias = PF...  Intersection table containing project fiscal years)
Table 4: PROJECT_FY_HEADCOUNT (Alias = PFH... Intersection table containing headcount per project and fiscal year)Please forgive the excessive normalization for this example, as I wanted to keep the table structure similar to my real application, which has much more going on.
In my sample, I have the "Select Criteria" region, where the user specifies the project and fiscal year range that he or she would like to report. Click the Search button, and the report returns the project headcount in a pivoted fashion for the fiscal year range specified.
I've got it working using a hard-coded query, which is displayed in the "Hardcoded Query" region. In this query, I basically return all years, and set conditions on each column which determines whether that column should be displayed or not based on the range selected by the user. While this works, it is not ideal, as there could be many more fiscal years to account for, and this is not very dynamic at all. Anytime a fiscal year is added to the FISCAL_YEAR table, I'd have to update this page.
So, after reading all of the OTN SQL pivot forums and "Ask Tom" pivot thread, I've been able to create a second region labeled "Dynamic Query" in which I've created a dynamic query to return the same results. This is a much more savvy solution and works great; however, the column names are generic in the report.
I had to set the query to parse at runtime since the column selection list is dynamic, which violates SQL rules. Can anyone please help me figure out how I can specify my column names in the dynamic query region to get the same column values I'm getting in the hardcoded region?
Please let me know if you need anymore information, and many thanks in advance!
Mark

Answer 1

Hi Tony,
Thanks so much for your response. I've had to study up on the dbms_sql package to understand your function... first time I've used it. I've fed my dynamic query to your function and see that it returns a colon delimited list of the column names; however, I think I need a little more schooling on how and where exactly to apply the function to actually set the column names in APEX.
From my test app, here is the code for my dynamic query. I've got it in a "PL/SQL function body returning sql query" region:
DECLARE 
  v_query      VARCHAR2(4000);
  v_as         VARCHAR2(4);
  v_range_from NUMBER;
  v_range_to   NUMBER;         
BEGIN
  v_range_from := :P1_FY_FROM;
  v_range_to   := :P1_FY_TO;
  v_query      := 'SELECT ';
  -- build the dynamic column selections by looping through the fiscal year range.
  -- v_as is meant to specify the column name as (FY10, FY11, etc.), but it's not working.
  FOR i IN v_range_from.. v_range_to  LOOP
    v_as    := 'FY' || SUBSTR(i, 3, 4);
    v_query := v_query || 'MAX(DECODE(FY_NB,' || i || ',PFH_HEADCOUNT,0)) '
      || v_as || ',';
  END LOOP;
  -- add the rest of the query to the dynamic column selection
  v_query := rtrim(v_query,',') || ' FROM ('
    || 'SELECT FY_NB, PFH_HEADCOUNT FROM ('
    || 'SELECT FY_ID, FY_NB FROM FISCAL_YEAR) A '
    || 'LEFT OUTER JOIN ('
    || 'SELECT FY_ID, PFH_HEADCOUNT '
    || 'FROM PROJECT_FY_HEADCOUNT '
    || 'JOIN PROJECT_FY USING (PF_ID) '
    || 'WHERE PL_ID = ' || :P1_PROJECT || ') B '
    || 'ON A.FY_ID = B.FY_ID)';
  RETURN v_query;
END;I need to invoke GET_QUERY_COLS(v_query) somewhere to get the column names, but I'm not sure where I need to call it and how to actually set the column names after getting the returned colon-delimited list.
Can you (or anyone else) please help me get a little further? Once again, feel free to login to my host account to see it first hand.
Thanks again!
Mark