Re: create function for trigger question - Mailing list pgsql-general

Barbera

What you have written is a stored procedure not a trigger function.
Trigger functions until 7.2 return generally OPAQUE and after 7.2 they
return TRIGGER. See the example of a trigger below for your function

CREATE OR REPLACE FUNCTION customer_bak_proc() RETURNS TRIGGER AS '
BEGIN
  IF TG_OP = ''DELETE'' THEN
      INSERT INTO customer_bak (id,name,value) VALUES
(OLD.id,OLD.name,OLD.value);
      RETURN NULL;
  END IF;

  IF TG_OP = ''UPDATE'' THEN
     INSERT INTO customer_bak (id,name,value) VALUES
(NEW.id,NEW.name,NEW.value);
     RETURN NEW;
  END IF;
  RETURN NULL;
END;' LANGUAGE 'plpgsql';

CREATE TRIGGER customer_bak_trigger AFTER DELETE OR UPDATE ON customers
FOR EACH ROW EXECUTE PROCEDURE customer_bak_proc();

What happens above is create the function then create the trigger on the
table and call the function based on what action occurred.

The function is in PL/PGSQL and it basically checks which operation and
then checks the OLD array if it is a delete operation or the NEW array
if it is an update operation.

NEW / OLD will hold all of the variables in the row that you just
updated / deleted and will access them via name and the dot (.) operator.

HTH
Darren


Barbara Lindsey wrote:

>I am a postgres newbie.
>
>I am trying to create a trigger that will put a copy of a record into a
>backup table before update or delete. As I understand it, in order to do
>this I must have a function created to do this task.
>The function I am trying to create is as follows:
>
>CREATE FUNCTION customer_bak_proc(integer)  RETURNS boolean as
>'INSERT INTO customer_bak  (SELECT * from customer where id = $1 )'
>LANGUAGE 'SQL';
>
>Whenever I try to create this function, I get an error on the return type,
>as follows:
>ERROR:  function declared to return boolean, but final statement is not a
>SELECT
>
>I have tried using text, integer, opaque, NULL, 0, 1.
>And I have tried omitting the "RETURNS" clause altogether, but none of
>these works.
>
>What is the return data type of an SQL INSERT statement? I think that
>would work (?), but I have not been able to find this in any of the
>documentation.
>
>Has anyone else successfully written a function to do an insert?
>Has anyone else written a trigger to accomplish this kind of task?
>Perhaps I am taking the wrong approach...
>Thank you for any help.
>Barb Lindsey
>
>
>
>
>
>
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