You need to eliminate hash join and Index scan.

With this query you can do that using INTERSECT AND EXCEPT

SELECT CustomerID

FROM #Purchase

WHERE ProductCode = 'A'

INTERSECT

SELECT CustomerID

FROM #Purchase

WHERE ProductCode = 'B'

EXCEPT

SELECT CustomerID

FROM #Purchase

WHERE ProductCode = 'C'

Or, this one using CTE AND JOINS:

;WITH CTE AS

(

SELECT CustomerID

FROM #Purchase

WHERE ProductCode = 'A'

GROUP BY CustomerID

)

,CTE2 AS

(

SELECT CustomerID

FROM #Purchase

WHERE ProductCode = 'B'

GROUP BY CustomerID

)

,CTE3 AS

(

SELECT CustomerID

FROM #Purchase

WHERE ProductCode = 'C'

GROUP BY CustomerID

)

select CTE.CustomerID from CTE

left join CTE3 ON

CTE.CustomerID = CTE3.CustomerID

where CTE.CustomerID in (SELECT CustomerID FROM CTE2)

AND CTE3.CustomerID IS NULL

GROUP BY CTE.CustomerID