Trigger function to know which fields are being updated

I am writing a trigger function. How can I know which fields are being
updated in the PL/SQL function?

For example I have a table here:

CREATE TABLE COMPANY (
   COMPANY_ID VARCHAR(10) NOT NULL,
   NAME VARCHAR(30),
   ADDRESS VARCHAR(30));

I want to write a trigger to block all update statements without updating
NAME. I tried the following code block and it doesn't work:

   IF TG_OP = ''UPDATE'' THEN
      IF NEW.NAME IS NULL THEN
         RAISE NOTICE ' Field NAME must be provided!';
      END IF;
   END IF;

Are there any functions like the Oracle's UPDATING() predicate?

Bernard Cheung

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