Help required in writing a query

Question

hi
Consider a table (ShogenValue) with following data:
Model_Id header_id Serial_no shogen_no si_val
4329 1 40001 A0001 1
4329 1 40001 B0001 2
4329 1 50300 B0001 3
4329 1 40001 C0001 4
4329 1 50300 C0001 5
4329 1 60001 C0001 6
Select
     si_val
From
     ShogenValue
Where
model_id = 4329
And
     header_id = 1
And
serial_no = '60001'
Is it possible to write a modified version of above query which will bring the following result:
Model_Id header_id Serial_no shogen_no si_val
4329 1 40001 A0001 1
4329 1 50300 B0001 3
4329 1 60001 C0001 6
Meaning if a record exists for a particular shogen_no (Shogen_no C0001 has value corrosponding to '60001' in above query), pick it up, if it
does not exist (Shogen_no B0001 does not have value corrosponding to '60001' in above case) then pick a record with one level less serial number ('50300' in above case) and so on.
Thanx
Regards
Omer Imtiaz

Answer 1

This should help, although it will probably not perform. Try it and see what the plan for it is.
SELECT
FROM
  shogenvalue sv,
  (SELECT
    max(serial_no) serial_no_max,
    shogen_no
  FROM
    shogenvalue
  WHERE
    model_id = 4329
    AND header_id = 1
    AND serial_no <= '60001'
  GROUP BY
    shogen_no
  ) svm
WHERE
  sv.serial_no = svm.serial_no_max
  AND sv.shogen_no = svm.shogen_no
;HTH,
Lennert