Update timestamp when row is updated in PostgreSQL

Question

In MySQL, we can execute this where it updates the column changetimestamp every time the row is changed:

create table ab (
  id int, 
  changeti         


        

Answer 1

Create a function that updates the changetimestamp column of a table like so:

CREATE OR REPLACE FUNCTION update_changetimestamp_column()
RETURNS TRIGGER AS $$
BEGIN
   NEW.changetimestamp = now(); 
   RETURN NEW;
END;
$$ language 'plpgsql';

Create a trigger on the table that calls the update_changetimestamp_column() function whenever an update occurs like so:

    CREATE TRIGGER update_ab_changetimestamp BEFORE UPDATE
    ON ab FOR EACH ROW EXECUTE PROCEDURE 
    update_changetimestamp_column();