Changing the query on a view object

Question

I have a view object right now, based on an entity. It is the default view object, so that means the query in the view object is straight forward, it grabs all of the attributes from the table. And there is no WHERE clause.
In reality I only want to show a finite set of rows from my table. Every time a record is changed/edited in this entity and committed, a new row in the database is created with the same information (I'm using CreateWithParams) except for a few columns.
I actually don't really have update on this table, just creation of new rows. But to the user, I want it to 'look' like they are editing something in the table.
Example:
12, 11:32,Thompson, 60 (the user edits this information in an adf table, and a new row is created in the db)
12, 11:55, Thompson, 75
I have a timestamp (see above) field in the database that is used as part of my primary key, so that I know which record is the latest.
When the VO query is run, I want the user to only see the latest row from the db.
12, 11:55, Thompson, 75
So...
I went to my VO, and I changed the WHERE query to add this:
where t1.TimeStamp = (Select MAX(t2.TimeStamp) FROM rcl.x t2 where t1.uid = t2.uid);
Now, this isn't a mysql/sql question. There's actually a better query that I'd rather run, but the VO editor doesn't allow me to change the query itself....
When I save the new WHERE to my VO, run my page again, I get the expected result (showing me only the latest records).
However, when I try and sort on the table in which my data is displayed, I am now getting ORDER BY errors.
I don't want my VO to be read-only sql based. I want to be able to update my table, so I have my VO running off of the entity.
Why doesn't the VO allow me to change the query itself? (Like do a subquery, instead of having my where clause do the work)
Why are order by errors being thrown when I sort on my adf table after changing the where clause in my view?
Hopefully I wasn't too convoluted in the explanation of my problem..
Thanks in advance,
Joel

Answer 1

HI Joe,
Regarding your problem you can do one of the following tasks:
1- easily to tuning on your view object, I mean in the tuning page of the view you can set that only return 1 record or 2-3 record fetch not all the record.
in the order by you will order by the timestamp field and descending.
2- you can order by the timestamp descending and in the where clause only set the rownum<2 (will return the last record) you can also set rownum<5 and get the 4 last record etc.
3-editing the view query in the expert mode is not advised at all because of many consequences that you will face.
4- maybe it is not bat that you add a readonly view for the table you mentioned and every time you unpdate the entity just re-execute the read-only view.( this method maybe is good maybe is not it depends on your business logic)
Regards.
Edited by: Amir Khanof on Sep 3, 2010 11:11 PM