SELECT 
	a.contactname as master_contactname,
	b.contactname as duplicate_contactname
FROM someTable as a
inner join someTable as b
	on a.Postcode = b.PostCode
WHERE a.ID < b.ID

CREATE PROCEDURE dbo.ProcName
	(@ID1 INT,
	@ID2 INT)
AS
BEGIN

	SELECT A.id,'EXACT'
	FROM sometable A
	CROSS APPLY sometable B
	WHERE A.ID=@id1
	AND B.id=@id2
	AND A.surname=B.surname
	AND A.firstname=B.firstname
		UNION
	SELECT A.id,'EXACT'
	FROM sometable A
	CROSS APPLY sometable B
	WHERE A.ID=@id1
	AND B.id=@id2
	AND A.middle=B.middle
		UNION 
	SELECT A.id,'LIKELY'
	FROM sometable A
	CROSS APPLY sometable B
	WHERE A.ID=@id1
	AND B.id=@id2
	AND (A.middle=NULL OR A.middle =''
	OR A.middle=NULL OR A.middle ='')
		
		etc .....
		

END

    <lastnames match="equal">
        
	<firstnames match="equal">
            <middlenames match="equal">sure</middlenames>
            <middlenames match="both_empty">sure</middlenames>
            <middlenames match="one_empty">sure</middlenames>
            <middlenames match="approx">likely</middlenames>
            <middlenames match="contains">likely</middlenames>
            <middlenames match="unequal">possible</middlenames>
        </firstnames>

        <firstnames match="sounds_equal">
            <middlenames match="equal">sure</middlenames>
            <middlenames match="both_empty">likely</middlenames>
            <middlenames match="one_empty">likely</middlenames>
            <middlenames match="approx">possible</middlenames>
            <middlenames match="contains">possible</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

        <firstnames match="both_empty">
            <middlenames match="equal">zero</middlenames>
            <middlenames match="both_empty">likely</middlenames>
            <middlenames match="one_empty">zero</middlenames>
            <middlenames match="approx">zero</middlenames>
            <middlenames match="contains">zero</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

        <firstnames match="one_empty">
            <middlenames match="equal">zero</middlenames>
            <middlenames match="both_empty">likely</middlenames>
            <middlenames match="one_empty">likely</middlenames>
            <middlenames match="approx">zero</middlenames>
            <middlenames match="contains">likely</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

        <firstnames match="approx">
            <middlenames match="equal">likely</middlenames>
            <middlenames match="both_empty">likely</middlenames>
            <middlenames match="one_empty">likely</middlenames>
            <middlenames match="approx">possible</middlenames>
            <middlenames match="contains">possible</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

        <firstnames match="sounds_approx">
            <middlenames match="equal">likely</middlenames>
            <middlenames match="both_empty">possible</middlenames>
            <middlenames match="one_empty">possible</middlenames>
            <middlenames match="approx">zero</middlenames>
            <middlenames match="contains">possible</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

        <firstnames match="contains">
            <middlenames match="equal">likely</middlenames>
            <middlenames match="both_empty">likely</middlenames>
            <middlenames match="one_empty">likely</middlenames>
            <middlenames match="approx">possible</middlenames>
            <middlenames match="contains">possible</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

        <firstnames match="unequal">
            <middlenames match="equal">zero</middlenames>
            <middlenames match="both_empty">zero</middlenames>
            <middlenames match="one_empty">zero</middlenames>
            <middlenames match="approx">zero</middlenames>
            <middlenames match="contains">possible</middlenames>
            <middlenames match="unequal">zero</middlenames>
        </firstnames>

    </lastnames>