I'm trying to isolate duplicate sale numbers and change the revenue dollar amount for just one of each duplicate sale number found to zero.
Anyone know how to do this? (Code and data set below)

Code:
SELECT dis.name AS
district_id,
  pat.account_number,
 Substr(pat.Sale_number,1,4) as Sale_Num,
  pat.sale_date,
  revenue_dollar_amount,
(select COUNT(*)
from district_tbl dis,
payroll_accrual_tbl pat
Where pat.district_id = dis.id
 AND pat.accrual_status_flag = 'P'
 AND '926103' = pat.district_id
AND pat.sale_number = pat.sale_number
HAVING COUNT(*) >= 1)
a
FROM district_tbl dis,
payroll_accrual_tbl pat
Where pat.district_id = dis.id
 AND pat.accrual_status_flag = 'P'
 AND '926103' = pat.district_id
AND pat.sale_number = pat.sale_number
25291 1478 15-FEB-07 3952.8 4
25291 1478 15-FEB-07 3952.8 4
22485 1479 15-FEB-07 2436.6 4
22485 1479 15-FEB-07 2436.6 4

So one 3952.8 would show 0 and one 2436.6 would show 0