Dynamic Query for a report

Question

Hi,
I have to generate a report which contains a query with database link. This database link is not hard coded and would be picked up from another report which contans a link to this report. So this database link value for the query could be any. Can anyone guide me hot to write a dynamic select statement so that i could append database link value at run time.
Thanks
Salman

Answer 1

Hi,
You can not directly use a PL/SQL query to create an Interactive Report - that is not yet available.
What you could do is create a collection from your query and then use that for the report. Have a look at: [http://download-uk.oracle.com/docs/cd/B32472_01/doc/appdev.300/b32471/advnc.htm#BABGHJFD].
In there, you will see APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY - this allows you to create a collection from a string. You could add a PL/SQL process to your page that runs "On Load: Before Header" that actually creates the collection. Something like:
BEGIN
IF APEX_COLLECTION.COLLECTION_EXISTS('MYCOLLECTIONNAME') THEN
  APEX_COLLECTION.DELETE_COLLECTION('MYCOLLECTIONNAME');
END IF;
APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY('MYCOLLECTIONNAME','MY SQL QUERY STRING');
END;Your Interactive Report can then be based on:
SELECT SEQ_ID, C001, C002, C003, ...
FROM APEX_COLLECTIONS
WHERE COLLECTION_NAME = 'MYCOLLECTIONNAME'The tricky part is the headings as these would tend to be the SEQ_ID, C001, C002, C003, etc column names from the collection itself.
To get around this, make sure that the report's sql statement includes as many Cnnn columns as you will need for the widest of the reports. Before doing anything else, run the report once to make sure that all these columns are included in the output.
Then, through Shared Components, Application Items, create items that will hold heading names - for example, G_HEADING1, G_HEADING2 etc - one for each possibile column.
Now, update the process to:
BEGIN
IF APEX_COLLECTION.COLLECTION_EXISTS('MYCOLLECTIONNAME') THEN
  APEX_COLLECTION.DELETE_COLLECTION('MYCOLLECTIONNAME');
END IF;
IF ..test1.. THEN
  APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY('MYCOLLECTIONNAME','MY SQL QUERY STRING 1');
  :G_HEADING1 := 'ColumnHeading1Value';
  :G_HEADING2 := 'ColumnHeading2Value';
  :G_HEADING3 := NULL; -- column not used for this query, so set it to null
ELSIF ..test2 .. THEN
  APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY('MYCOLLECTIONNAME','MY SQL QUERY STRING 2');
  :G_HEADING1 := 'ColumnHeading1Value';
  :G_HEADING2 := 'ColumnHeading2Value';
  :G_HEADING3 := 'ColumnHeading3Value';
ELSIF ...etc...
  .. etc ...
END IF;
END;Finally, on the report itself, set the column headings to *&G_HEADING1.*, *&G_HEADING2.* etc. Then, on each column, set a Condition of "Value of Item in Expression 1 is NOT NULL" and in Expression 1, enter in the application item for that column - eg, G_HEADING1
I have done all that here: [http://apex.oracle.com/pls/otn/f?p=16338:5] - select either Departments or Employees from the list and the report will change.
Andy