Updating a column

Question

I have a column that I am updating in a table using two udpate scripts because I am converting several tables to one table and the column and some data has one key I need to use to update and other data has another key. However, when I run one it clears out the column updated by the other and vice versa. Can someone tell me what I am doing wrong? It doesn not matter which update runs first or second. The udpates are:
UPDATE SERIAL_COMPNT_ALLOW_COPY t1
SET serialized_compnt_id =
     (SELECT
     serialized_compnt_id
          FROM SERIALIZED_COMPNT t2
          WHERE t2.cmpny_part_nbr = t1.cmpny_part_nbr
AND t2.serial_nbr = t1.serial_nbr
          AND t1.cmpny_part_nbr NOT LIKE 'ENG%'
          AND t2.cmpny_part_nbr NOT LIKE 'ENG%'
COMMIT;
and
UPDATE SERIAL_COMPNT_ALLOW_COPY t1
SET serialized_compnt_id =
     (SELECT
     serialized_compnt_id
          FROM SERIALIZED_COMPNT t2
          WHERE t2.cmpny_part_nbr = t1.cmpny_part_nbr
AND t2.serial_nbr = DECODE(SUBSTR (t1.serial_nbr,1,1),'0',SUBSTR(t1.serial_nbr,2,15), t1.serial_nbr)
          AND t1.cmpny_part_nbr LIKE 'ENG%'
          AND t2.industrial_item_nbr = '000'
COMMIT;
Thank you.

Answer 1

You probably need to add WHERE EXISTS clauses to your updates. Like this...
UPDATE SERIAL_COMPNT_ALLOW_COPY t1
SET    serialized_compnt_id =
             (SELECT serialized_compnt_id
              FROM   SERIALIZED_COMPNT t2
              WHERE  t2.cmpny_part_nbr = t1.cmpny_part_nbr
              AND    t2.serial_nbr = t1.serial_nbr
              AND    t1.cmpny_part_nbr NOT LIKE 'ENG%'
              AND    t2.cmpny_part_nbr NOT LIKE 'ENG%'
WHERE EXISTS (SELECT serialized_compnt_id
              FROM   SERIALIZED_COMPNT t2
              WHERE  t2.cmpny_part_nbr = t1.cmpny_part_nbr
              AND    t2.serial_nbr = t1.serial_nbr
              AND    t1.cmpny_part_nbr NOT LIKE 'ENG%'
              AND    t2.cmpny_part_nbr NOT LIKE 'ENG%'
;