Re: Can this be done with a trigger?

artmerar_at_yahoo.com wrote:
> On Aug 5, 11:43 am, gazzag <gar..._at_jamms.org> wrote:
> > On 5 Aug, 17:11, artme..._at_yahoo.com wrote:
> >
> >
> >
> > > Hi,
> >
> > > We have a table like this:
> >
> > > CUSTOMER_ID
> > > PRODUCT_ID
> > > FORMAT
> > > STATUS
> > > DATE_ADDED
> > > DATE_MODIFIED
> >
> > > We also have a history table like this:
> >
> > > CUSTOMER_ID
> > > PRODUCT_ID
> > > FORMAT
> > > STATUS
> > > SOURCE
> > > DATE_ADDED
> >
> > > We want to put a trigger on the first table such that when a record is
> > > inserted or updated it will make the entry to the history table.
> > > However, the problem is the 'SOURCE' column on the history table. It
> > > is not present or needed in the first table.
> >
> > > Entries into the first table are done through a PL/SQL program. So,
> > > what we want is that when the entry is made into the first table, it
> > > fires the trigger to make the second entry. But, how can this be done
> > > if the columns do not match?
> >
> > > We do not want to code it in the PL/SQL program because then someone
> > > can make an entry to the first table and we cannot record the history
> > > on it, yet the SOURCE column only gets populated in the PL/SQL
> > > program....
> >
> > > And, to make things more complicated, depending on what is being
> > > UPDATED, we may need the values of :NEW or :OLD........
> >
> > > Is there a way to do this?
> >
> > Sure there is. What is SOURCE though?

> Gazzag,

> I am trying to write the trigger. Problem is since you cannot pass
> parameters to triggers, where does the trigger get the value for
> SOURCE? All I can think of is to update the record from the PL/SQL
> procedure once the trigger gets done........

> So, say I have a procedure like this:

> PROCEDURE ADD (
> p_customer_id NUMBER,
> p_product_id VARCHAR2,
> p_source VARCHAR2 DEFAULT 'U') IS

> INSERT INTO customer_config
> VALUES (p_customer_id, p_product_id, 'Text', 'Active', SYSDATE);

> The SOURCE is not needed in this table. But, this would fire the
> trigger where SOURCE is needed. The SOURCE will be derived within the
> PL/SQL code. I do not think this is possible. I may have to let the
> trigger fire, then go back and update the row.....

And if someone inserts a row in the table without using the PL/SQL program (the scenario you were worried about above), how does SOURCE get populated? The trigger has to be able to assume a value for SOURCE, or this will not work.

-- 
_______________________________________________________________________
Dan Blum					         tool_at_panix.com	
"I wouldn't have believed it myself if I hadn't just made it up."