CREATE OR REPLACE FORCE VIEW CCS3.NON_BILLABLE_ACCOUNTS2
(
   fname,
   lname
)
AS
   SELECT *
     FROM (CASE when get_flag('switch_table')=0
   (
   SELECT    fname,
                 lname
     FROM T1 t1, T2 t2
    WHERE t1.t1_id = t2.t2_id
    )

    else
    (
      SELECT    fname,
                    lname
     FROM P1 p1, P2 p2
    WHERE p1.p1_id = p2.p2_id
    )
);

create view twotab as
select ename from emp where get_flag=1
union all
select dname from dept where get_flag=0;

CREATE OR REPLACE FUNCTION "GET_FLAG" ( IN_FLAG_NAME IN FLAGS.NAME%TYPE ) RETURN FLAGS.VALUE%TYPE IS
 l_RESULT FLAGS.VALUE%TYPE;
BEGIN
  SELECT VALUE INTO l_RESULT FROM FLAGS WHERE NAME = IN_FLAG_NAME;

  RETURN l_RESULT;
END;
/

create view twotab as
select ename from emp where sys_context('MyAppCtx','SWITCH_TABLE') != '0'
union all
select dname from dept where sys_context('MyAppCtx','SWITCH_TABLE') = '0';