Performance tuning OLTP query I have the following SQLs executed millions of times a day, a single execution isn't an issue but executing million times is causing some performance issues..Thanks in advance for your help!

NOTE: data can change in any of the tables any time during the day..can't reduce number of executions and this is Oracle 11g env.

SELECT COUNT (*)
    INTO v_cnt
  FROM t1 cpr, t2 brl
 WHERE cpr.cp_id = :1
     AND cpr.brl_id = brl.brl_id
     AND brl.ranking &gt; 0
     AND cpr.security_enabled_ind='Y'
     AND cpr.brl_id NOT IN (
                   SELECT rpr.brl_id
                     FROM t3 rpr, t4 ppr, t5 plcy
                    WHERE rpr.ppr_id = ppr.ppr_id
                      AND ppr.plcy_id = plcy.plcy_id
                      AND plcy.db_object_name = :2);
IF v_cnt = 0
THEN

SELECT where_clause
  FROM
    (SELECT where_clause
       FROM t4 ppr_o
     WHERE ppr_o.ppr_id IN (
                    SELECT ppr.ppr_id
                      FROM t1 cpr,
                           t3 rpr,
                           t4 ppr,
                           t5 plcy
                     WHERE cpr.cp_id = :1 
                        AND cpr.brl_id = rpr.brl_id
                        AND rpr.ppr_id = ppr.ppr_id
                        AND ppr.plcy_id = plcy.plcy_id
                        AND cpr.security_enabled_ind='Y'
                        AND plcy.db_object_name = :2
                        AND plcy.statement_type = :3)
    ORDER BY NVL (ppr_o.ranking, 0) DESC)
WHERE ROWNUM = 1;
END IF;


Number of records


t1 -> 205101
t2 -> 42
t3 -> 142
t4 -> 57
t5 -> 13
I would first consider trying to combine the two queries into one. If the second query could be refactored to return null in the case where the first query returned zero would you be able to work with that?

For example,

testbed:

create table t1( cp_id integer, 
                 brl_id integer, 
                 security_enabled_ind char(1) );
create table t2( brl_id integer, 
                 ranking number );
create table t3( ppr_id integer,
                 brl_id integer );
create table t4( ppr_id integer, 
                 plcy_id integer, 
                 where_clause varchar(1000), 
                 ranking number );
create table t5( plcy_id integer, 
                 db_object_name varchar(100), 
                 statement_type integer );


refactored query:

with w as ( select rpr.brl_id, ppr_id, plcy.statement_type
            from t3 rpr join t4 ppr using(ppr_id) join t5 plcy using(plcy_id)
            where plcy.db_object_name=:2 )
select where_clause
from( select where_clause
      from t4 ppr_o
      where not exists ( select *
                         from t1 cpr join t2 brl using(brl_id)
                         where cpr.cp_id = 1 and brl.ranking &gt; 0
                               and cpr.security_enabled_ind='Y'
                               and brl_id not in (select brl_id from w) )
            and ppr_o.ppr_id in ( select ppr_id
                                  from t1 cpr join w using(brl_id)
                                  where cpr.cp_id=:1
                                        and cpr.security_enabled_ind='Y'
                                        and w.statement_type=:3 )
    order by ppr_o.ranking desc nulls last )
where rownum=1;