create table opCodeType
	(opCodeTypeID tinyint
	,opCodeTypeDesc varchar(50))
go
create table myTable
	(PatientID int
	,Opdate datetime
	,OpCode int
	,OpCodeTypeID tinyint references opCodeType(opCodeTypeID))

go

insert opCodeType values (1, 'Primary')
insert opCodeType values (2, 'Secondary')
go

--then your query could be something like:

select	patientID
	,opDate
	,opCode
	,opCodeTypeDesc
from	myTable a
join	(--derived table to get first date for each Patient
	select	patientID
		,min(opDate) opDate 
	from	myTable 
	group by patientID
	) b
		on a.patientID = b.patientID
		and a.opDate = b.opDate
join	opCodeType c
		on a.opCodeTypeID = c.opCodeTypeDesc