To find all rows that are in dbo.TABLE1 but not in dbo.TABLE2 using the SQL JOIN operator:

SELECT              COUNT(*)
FROM                dbo.TABLE1 t1 WITH (NOLOCK)
LEFT OUTER JOIN     dbo.TABLE2 t2 WITH (NOLOCK)
ON                  t1.PrimaryKey = t2.PrimaryKey
WHERE               t2.PrimaryKey IS NULL