SQL & PL/SQL

So I have a one to many join where the SMOPERATOR table has data I need however it has a couple of rows that match the JOIN condition in there. I just need to return one row. I think this can be accomplished with a subquery in the join however have not been able to come up with the right syntax to do so.

So:

SELECT "NUMBER" as danumber,
NAME,
SMINCREQ.ASSIGNMENT,
SMOPERATOR.PRIMARY_ASSIGNMENT_GROUP,
SMOPERATOR.WDMANAGERNAME,
SMINCREQ.owner_manager_name,
SMINCREQ.subcategory, TO_DATE('01-'||TO_CHAR(open_time,'MM-YYYY'),'DD-MM-YYYY')MONTHSORT,
(CASE WHEN bc_request='f' THEN 'IAIO'
WHEN (bc_request='t' and substr(assignment,1,3)<>'MTS') THEN 'RARO'
WHEN (bc_request='t' and substr(assignment,1,3)='MTS') THEN 'M'
ELSE 'U' end) as type

from SMINCREQ
left outer join SMOPERATOR on SMINCREQ.assignment=SMOPERATOR.primary_assignment_group

WHERE SMINCREQ.owner_manager_name=:P170_SELECTION and SMOPERATOR.wdmanagername=:P170_SELECTION
AND open_time BETWEEN to_date(:P170_SDATEB,'DD-MON-YYYY') AND to_date(:P170_EDATEB,'DD-MON-YYYY')
AND
(
(bc_request='f' and subcategory='ACTIVATION' and related_record<>'t')
OR
(bc_request='f' and subcategory<>'ACTIVATION')
OR
(bc_request='t' and substr(assignment,1,3)<>'MTS')
)
order by OPEN_TIMe