variables in if conditions

[prodadmin]

can we use variables in if conditions
if( 0 <> P_COMPANY_ID ) and
(P_COMPANY_ID = COMPANY_ID)

if( 0 <> P_JOB_ID )
(P_JOB_ID = CODING_JOB_ID)


or use variables to assign some thing in SQL stmt

select CODING_JOB_ID, PATH
from CODING_JOBS
where CODING_STAGE_ID in (2,6)
and "" <> P_RESERVED_CODER_ID
and (P_RESERVED_CODER_ID = RESERVED_CODER_ID)


here is the actual code where
FUNCTION FN_AVAILABLE
( P_USER_ID in USERS.MEMBER%TYPE
,P_PASSWORD in MEMBERS.password%TYPE
,P_RESERVED_CODER_ID in USERS.MEMBER%TYPE
,P_JOB_ID in CODING_JOBS.CODING_JOB_ID%TYPE
,P_COMPANY_ID in CODING_JOBS.COMPANY_ID%TYPE
)
RETURN RECORDSET IS
Result RECORDSET;
BEGIN
L_MT_ID = PA_C.FN_MID( P_USER_ID);
if PA_wc.f_VMt( L_MT_ID, P_PASSWORD) then

--OPEN Result FOR
select CODING_JOB_ID,
PATH
from CODING_JOBS
where CODING_STAGE_ID in (2,6)
and ( RESERVED_CODER_ID=" " OR P_RESERVED_CODER_ID = RESERVED_CODER_ID)
and (COMPANY_ID=0 OR P_COMPANY_ID = COMPANY_ID)
and (CODING_JOB_ID=0 OR P_JOB_ID = CODING_JOB_ID);

end if;

return( Result);

END FN_AVAILABLE;

in the above sql stmt i would like to assign values to variables
Is this works!!

any help is much appreciated