Trigger In PostgreSQL

Create a Trigger

CREATE OR REPLACE TRIGGER add_sms_retry_time

BEFORE UPDATE 

ON public.sms_pool

FOR EACH ROW

EXECUTE PROCEDURE public.add_sms_try_time();

Define the Trigger Function

CREATE OR REPLACE FUNCTION update_modified_column()

RETURNS TRIGGER 

LANGUAGE PLPGSQL

AS

$$

BEGIN

IF row(NEW.a2wackid) IS DISTINCT FROM row(OLD.a2wackid) THEN

NEW.last_try = now()::TIMESTAMP; 

NEW.try_time = concat(OLD.try_time ,', ', to_char(now(), 'DD/MM/YY HH24:MI:SS'));

NEW.retry = OLD.retry - 1;

END IF;

RETURN NEW;

END;

$$

Remove Trigger and Function 

DROP TRIGGER add_sms_retry_time ON sms_pool

DROP FUNCTION add_sms_try_time()

View the Function Body

SELECT proname,prosrc FROM pg_proc WHERE proname= 'update_modified_column';