Merging columns in SQL query based on the certain criteria

Hi,

I find query below:

SELECT AL1.BILL_NO as "Bill No", AL3.MAIN_TYPE as "Main Type", AL3.BILL_NO as "Bill No",
AL3.SUB_TYPE as "Sub Type", AL3.AMOUNT as "Amount", AL2.PAY_ID as "Pay ID"

FROM TABLE1 AL1, TABLE2 AL2, TABLE3 AL3, TABLE4 AL4, TABLE5 AL5
WHERE (AL1.BILL_NO = AL4.BILL_NO (+) AND  AL1.REF_NO = AL5.REF_NO (+) AND
AL1.BILL_NO=AL2.BILL_NO AND AL4.ID=AL3.ID)

This query is returning the duplicate records. What I want is if Bill No and MAIN TYPE is same, then it should combine SUB TYPE to avoid counting of duplicate records.

Thanks