merge in postgres trigger function

Hello,

I am trying to move few objects to postgres from oracle.

I have an issue with a trigger, which has a merge inside?

Here is my code:

BEGIN

    MERGE INTO Requests r

                                                using (select new.web_form_id web_form_id,

                                                                                                                                                  new.form_type form_type,

                                                                                                                                                  new.submit_date submit_date,

                                                                                                                                                  new.email email,

                                                                                                                                                  new.custom_fields custom_fields

                                                                                                                 from   DUAL) w

                                                                  on         (r.request_id = new.web_form_id)

                                when not matched

                                THEN

                                                insert                                                      (

                                                                                                                                                                                r.request_id,

                                                                                                                                                                                r.form_type,

                                                                                                                                                                                r.submit_date,

                                                                                                                                                                                r.request_email,

                                                                                                                                                                                r.request_description

                                                                                                                                                  )

                                                                 values  (

                                                                                                                                  w.web_form_id,

                                                                                                                                  w.form_type,

                                                                                                                                  w.submit_date,

                                                                                                                                  w.email,

                                                                                                                                  w.custom_fields

                                                                                                                 )

                                when matched

                                then

                                                update set

                                                                form_type = NVL (w.form_type, r.form_type),

                                                                submit_date = NVL (w.submit_date, r.submit_date),

                                                                request_email = NVL (w.email, r.request_email),

                                                                request_description = NVL (w.custom_fields, r.request_description);

                end if;

END;

I receive an error – “Requests is not a known variable, Line 3: MERGE INTO Requests r”

But “Requests” is a table is not a variable!

What is wrong with my statement? May be Merge is not legal in postgres trigger functions?

What would be the way around?

Thank you,

Leon

leon.match@convergia.net