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(dot)match(at)convergia(dot)net