Question

I want to run a trigger when I update a certain field on the database, so it updates another field (basically we have 2 different unique IDs for each record, so when one is changed, we need to update the other too – yay!)

CREATE OR REPLACE TRIGGER trigger_name ON table AFTER
  UPDATE AS
  UPDATE table A
  SET unique_to_update = NVL(
    (SELECT b.unique_to_update_from
    FROM table b
    WHERE B.other_unique_id = A.unique_id_to_match
    ), 0);

I have no idea if this works (scared to test it, quite frankly, since I’m certain it’ll break things) and even if it did, it’d run on every single update of that table – not just the one field that I wanted.

Any help would be much appreciated, thank you!

Answer 1

Test anything before putting it in production.

Something like this shoud be your trigger:

CREATE OR REPLACE TRIGGER trigger_name  
BEFORE UPDATE of unique_id_to_match
ON table
FOR EACH ROW
AS
BEGIN
  select 
    NVL(
      (SELECT b.unique_to_update_from
      FROM table b
      WHERE B.other_unique_id = :new.unique_id_to_match
      ), 0)
   into :new.unique_to_update 
   FROM dual;
END;