How can i optimize this query, 
how to rewrite a request through exists:

```
select DISTINCT 
        p.SBJ_ID, 
    nvl(l.ATTR,c.CODE) as ATTR, 
        l.VALUE
from T_TRFPRMLST p,
       T_CMSATTR_LINK l, 
       C_SBJCONCEPT c
where l.SBJ_ID(+) = p.SBJ_ID
  and p.sbj_id = c.ID;

```