CREATE OR REPLACE TRIGGER trigger_name
BEFORE UPDATE OR INSERT
ON tab_name
FOR EACH ROW
BEGIN
Merge into ... ;
END;
create or replace trigger Test
after insert
on a1
for each row
declare
-- local variables here
nCount number:=0;
begin
if inserting then
select count(*) into nCount from a2 where id=:new.id;
if nCount > 0 then
update....
else
insert.....
end if;
end if;
end Test;
