Problem with NOT IN and Sub-Select

[mike <mike@xxxxxxxxxxxxxxxxxxx>]

I have the following query

SELECT vw_mail_add.contact_id, vw_mail_add.first_name,
vw_mail_add.last_name, vw_mail_add.address1, vw_mail_add.add2,
vw_mail_add.add3, vw_mail_add.add4, vw_mail_add.add5, vw_mail_add.add6
FROM vw_mail_add JOIN tb_contact_role ON vw_mail_add.contact_id =
tb_contact_role.contact_id WHERE tb_contact_role.type2 = 72 AND
tb_contact_role.contact_id NOT IN ( SELECT contact_id FROM
tb_contact_role WHERE  type2 <> 72);

which gives

 contact_id | first_name | last_name | address1 | add2 | add3 | add4 |
add5 | add6
------------+------------+-----------+----------+------+------+------
+------+------
(0 rows)


(aim is to select all records which do not appear in a different
category)

However if I two tables from the queries and do a right join I get 
SELECT DISTINCT
tb_client_list1.contact_id,tb_client_list2.contact_id,tb_client_list1.type2 FROM tb_client_list1 RIGHT JOIN tb_client_list2 ON tb_client_list1.contact_id=tb_client_list2.contact_id WHERE tb_client_list1.contact_id IS NULL ORDER BY tb_client_list2.contact_id;

196 rows

Anyone any idea what is going wrong here?


---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
      joining column's datatypes do not match