Insert into table only where record does not already exists, and source table is the same as destination table

Hi I'm trying to insert data into to a table, by "copying" most of the data from the same table
This script works only if the record does not already exist.

INSERT INTO BOM (PART_NO, ISSUE, REV, C_TYPE, COMP_PART_NO, POS)
SELECT '195N2106', ISSUE, REV, C_TYPE, COMP_PART_NO, POS FROM BOM  -- The new PART_NO to be created
WHERE PART_NO = '195N2131'                                                                   -- The old PART_NO to copy from
AND ISSUE = 6
AND REV = 3

If I have to create a new PART_NO in this BOM table, and I know that it should contain the same components as the "sum" of 2 other PART_NO's (all from one, plus all from a second that differs from the first), then I could use the script mentioned above for the first run  (copying from the first old PART_NO) but when I run the second time (copying from the second old PART_NO) it will fail because there will be duplicates.

Can anyone tell me how to rewrite this script so it will just skip/ignore the insert statement when a record allready exists..

Thanks in advance

Best regards

Stefan Bruhn
Stefan_BruhnAsked:
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morphmanCommented:

procedure proc1(V_IN_PARAM char, V_IN_ISSUE number, V_IN_REV number) is

v_count number(1) := 0;

begin

SELECT count(*) FROM BOM  
into v_count
WHERE PART_NO = V_IN_PART_NO
AND ISSUE = V_IN_ISSUE
AND REV = V_IN_REV

if v_count > 0 then
    INSERT INTO BOM (PART_NO, ISSUE, REV, C_TYPE, COMP_PART_NO, POS)
    SELECT '195N2106', ISSUE, REV, C_TYPE, COMP_PART_NO, POS FROM BOM
    WHERE PART_NO = V_IN_PARAM  
    AND ISSUE = V_IN_ISSUE
    AND REV = V_IN_REV
end if;

end proc1;
/

And then process

exec proc1(part_no);

Sorted.

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DanielztCommented:

try this.

INSERT INTO BOM (PART_NO, ISSUE, REV, C_TYPE, COMP_PART_NO, POS)
SELECT '195N2106', ISSUE, REV, C_TYPE, COMP_PART_NO, POS FROM BOM  WHERE PART_NO = '195N2131'                                                                  
AND ISSUE = 6
AND REV = 3
and not exist (select 1 from BOM where PART_NO = '195N2106')
DanielztCommented:
sorry.

a little change:

INSERT INTO BOM (PART_NO, ISSUE, REV, C_TYPE, COMP_PART_NO, POS)
SELECT '195N2106', ISSUE, REV, C_TYPE, COMP_PART_NO, POS FROM BOM  WHERE PART_NO = '195N2131'                                                                  
AND ISSUE = 6
AND REV = 3 and rownum=1
and not exists (select 1 from BOM where PART_NO = '195N2106')

this SQL will make sure insert 1 records no matter how many old records existing.
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