Oracle mesclar constantes em uma única tabela

merge into data
using (
    select
        'someid' id,
        'testKey' key,
        'someValue' value
    from
        dual
) val on (
    data.id=val.id
    and data.key=val.key
)
when matched then 
    update set data.value = val.value 
when not matched then 
    insert (id, key, value) values (val.id, val.key, val.value);