Postgresql Current timestamp on Update

Question

What is the postgres equivalent of the below mysql code

CREATE TABLE t1 (
  created TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  modified TIMESTAMP DEFAULT CURRENT         


        

Answer 1

Thank you for the information Mithun and Alex Brasetvik.

I'd like to add one minor tweak to the trigger. Since we mostly likely want the modified column to store the timestamp when the row was last changed, not when it was the target of an UPDATE statement, we have to compare the new and the old value of the row. We update the modified column only if these two values differ.

CREATE OR REPLACE FUNCTION update_modified_timestamp() RETURNS TRIGGER 
LANGUAGE plpgsql
AS
$$
BEGIN
    IF (NEW != OLD) THEN
        NEW.modified = CURRENT_TIMESTAMP;
        RETURN NEW;
    END IF;
    RETURN OLD;
END;
$$;

This trigger ensures that the modified column is updated only if the UPDATE operation actually changes the values stored in the row.