PostgreSQL add `create_at` and `updated_at` columns

add_timestamps.sql

ALTER TABLE __table_name__ ADD COLUMN created_at TIMESTAMP;
ALTER TABLE __table_name__ ALTER COLUMN created_at SET DEFAULT now();

CREATE OR REPLACE FUNCTION trigger_set_updated_at()
RETURNS TRIGGER AS $$
BEGIN
	NEW.updated_at=now();
	RETURN NEW;
END;
$$ LANGUAGE plpgsql;

ALTER TABLE __table_name__ ADD COLUMN updated_at TIMESTAMP;
ALTER TABLE __table_name__ ALTER COLUMN updated_at SET DEFAULT now();

-- DROP TRIGGER set_timestam ON testing;
CREATE TRIGGER trigger_set_updated_at
BEFORE UPDATE ON __table_name__
FOR EACH ROW
EXECUTE PROCEDURE trigger_set_updated_at();