better way

Is there a better way to write this:

SELECT a.oid_fld FROM for_payment a
WHERE a.serial_fld <> 2
AND EXISTS
(SELECT b.char_fld FROM for_payment b
WHERE b.serial_fld = 2
AND b.char_fld = a.char_fld)

Table for_payment
+-------------+------------+-----------+
| serial_fld | char_fld | oid_fld |
+-------------+------------+-----------+
| 1 | test1 | 456701 |
| 2 | test1 | 456702 |
| 3 | test1 | 456703 |
| 4 | test2 | 456704 |
| 5 | test3 | 456705 |
+-------------+------------+-----------+

sample problem:
Assuming that I pick 2 in serial_fld.
How do I get the oid_fld of the rows with char_fld equal
to the char_fld of 2?
I should get these:

+-----------+
| oid_fld |
+-----------+
| 456701 |
| 456702 |
+-----------+

Thanks.