UPSERT til tabel med dynamisk tabelnavn

MERGE fungerer perfekt med Native dynamisk SQL (EXECUTE IMMEDIATE):

create table so_test(pk number not null primary key, value varchar2(20));

insert into so_test(pk, value) values(1, 'one');

declare
  l_SQL varchar2(4000);
  l_tablename varchar2(4000) default 'so_test';
begin
  l_SQL := 'merge into ' || l_tablename || ' target' ||
    ' using (select 1 pk, ''eins'' value from dual union all
             select 2 pk, ''zwei'' value from dual) source
      on (target.pk = source.pk)
      when matched then 
        update set target.value = source.value
      when not matched then
        insert values(source.pk, source.value)      
  ';
  dbms_output.put_line(l_sql);
  execute immediate l_SQL;
end; 

Kan du venligst sende den fejlmeddelelse, du får, når du bruger MERGE?