Question

我正在PostgreSQL中设置触发器，我不确定如何确定某些情况。例如，我设置了表胶片，并且某些端点更改了在更改前行进行编辑时应创建精确副本的任何部分，并将其保存到films_log。而且，如果几行更改，我也需要这些行也记录下来。

CREATE TABLE films (
  id          integer PRIMARY KEY,
  title       varchar(40) NOT NULL,
  did         integer NOT NULL,
  date_prod   date,
  kind        varchar(10)
);


CREATE TABLE films_log (
  serial      integer,
  title       varchar(200),
  did         integer,
  date_prod   date,
  kind        varchar(200)
);

CREATE TRIGGER films_logging_trigger 
  BEFORE UPDATE ON myschema.films 
  FOR EACH ROW EXECUTE PROCEDURE films_logging();

我尝试过的事情：

CREATE OR REPLACE FUNCTION films_logging() RETURNS trigger
            LANGUAGE plpgsql
            AS $$
            BEGIN
            INSERT INTO films_log (id, title, did, date_prod, kind)
            SELECT id, title, did, date_prod, kind FROM films WHERE id = OLD.id
            END;
            $$;

Answer 1

Trigger functions have to return a row. In a before trigger, that is usually the new row.

You also don't need the SELECT, using the values from the old row directly is more efficient:

CREATE OR REPLACE FUNCTION films_logging() RETURNS trigger
  LANGUAGE plpgsql
AS $$
BEGIN
  INSERT INTO films_log (id, title, did, date_prod, kind)
  values (old.id, old.title, old.did, old.date_prod, old.kind);

  return new; --<< here
END;
$$;

创建触发器的复制过程

1 个答案: