gistfile1.sql

merge /*+ index(e ext_val_pk6) use_nl(e) string*/
into ext_values  e
using (select ? txn_id, ? exn_id, ? ext_value from fastdual) d
on (e.txn_id = d.txn_id and e.exn_id = d.exn_id)
when matched then update set ext_value = d.ext_value
when not matched then insert (txn_id, exn_id, ext_value) values (d.txn_id, d.exn_id, d.ext_value)