SQL group get first record (sql+oracle)

SQL version

SELECT * FROM
(Select T.closedate,t.expirydate,t.datatypelookupid,
Row_number () over (partition by Closedate,expirydate,datatypelookupid ORDER by Closedate,expirydate,datatypelookupid)
As New_index
FROM dbo. Indexvolatilitymarketdata T
) A Where a.new_index=1

Oracle version

SELECT * FROM (
Select T.as_of_date,t.origination_date,t.maturity_date,
Rank () over (partition by t.as_of_date,t.origination_date,t.maturity_date order by T.as_of_date,t.origination_date, t.maturity_date) mm from Alm_agreement_deposit t) a
where A.mm=1;

SQL group get first record (sql+oracle)