SELECT a.FNAME, a.LNAME, a.DOB

, b.[Address], b.City, b.[State], ISNULL(b.P#, a.P#) AS P#

FROM @Table1 a

INNER JOIN @Table2 b

ON (a.P# = b.P#)

OR (

((a.P# IS NULL)

OR (b.P# IS NULL))

AND (a.FNAME = b.FNAME)

AND (a.LNAME =...