Sort of Complex Query - Howto Eliminate Repeating Results

they query i'm using is as follows:

SELECT t_product.product_id,
       t_product.product_number,
       t_serial_number.serial_number_id,
       t_serial_number.serial_number,
FROM t_serial_number
LEFT JOIN t_link_contract_number_job_number
    ON (
t_serial_number.link_contract_number_job_number_id =

t_link_contract_number_job_number.link_contract_number_job_number_id
       )
LEFT JOIN t_job_number
   ON (
t_link_contract_number_job_number.job_number_id =
        t_job_number.job_number_id
      )
LEFT JOIN t_product
   ON ( t_product.product_id =
        t_job_number.product_id
      )
LEFT JOIN t_inspect
   ON ( t_serial_number.serial_number_id =
        t_inspect.serial_number_id
      )
LEFT JOIN t_inspect_area
   ON ( t_inspect.inspect_area_id =
        t_inspect_area.inspect_area_id
      )
WHERE t_serial_number.serial_number_id NOT IN
      (SELECT serial_number_id FROM t_inspect
       WHERE t_inspect_area.inspect_area_id = 2
       AND inspect_pass = true)
       OR t_inspect_area.inspect_area_id IS NULL
ORDER BY serial_number::int ASC

my last problem is that serial number repeats for each
inspection.  let's say 2/n has four fails w/o a pass.
it will display four rimes.  i want it to display a
single time.  select distinct didn't work.  i don't
know if it is possible to get distinct values withing
an ON clause.

i need to check all 4 inspections (for same serial
number) to see if one of them is a pass, but i only
want to display a single serial number if there is no
pass (or if it is null - inspection not completed
yet).

tia...

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