postgresql 触发器错误控制在没有 RETURN 的情况下到达触发器末尾

Question

编辑：我已将更新后的代码添加到我的 post，但我缺少一个 return null 在我的 IF 块之外

我有一个包含最新数据的 table working，我想添加一个触发器来更新它，这样我就可以在另一个 table history。我运行这段代码创建了一个触发器函数并对其进行了测试，但出现错误

SQL Error [2F005]: ERROR: control reached end of trigger procedure without RETURN
  Where: PL/pgSQL function update_history()

我的代码：

-- create function for updates to track history
CREATE function update_history ()
RETURNS TRIGGER
as $$
BEGIN   
    IF NEW.discipline <> OLD.discipline THEN
    INSERT INTO history
        (ShiftId, fieldName, OldValue, NewValue)
    VALUES(New.shift_id, 'discipline', OLD.discipline, NEW.discipline);
    END IF;
return null; -- notice return outside the IF block
END;
$$
language plpgsql;


-- create trigger for my table after updates are made to the working table
create trigger update_history_trigger
after update on working
for each row execute PROCEDURE update_history();

Answer 1

当条件不满足时，您的函数无法到达 RETURN 语句。将语句放在 IF 块之外。返回值将被忽略，您可以使用 NULL 而不是 NEW.

CREATE FUNCTION update_history ()
RETURNS TRIGGER
AS $$
BEGIN
    IF NEW.discipline <> OLD.discipline THEN
        INSERT INTO history (ShiftId, fieldName, OldValue, NewValue)
        VALUES(NEW.shift_id, 'discipline', OLD.discipline, NEW.discipline);
    END IF;
    RETURN NULL;
END;
$$
LANGUAGE plpgsql;

每 the documentation:

The return value of a row-level trigger fired AFTER or a statement-level trigger fired BEFORE or AFTER is always ignored; it might as well be null.

postgresql 触发器错误控制在没有 RETURN 的情况下到达触发器末尾

postgresql trigger error control reached end of trigger without RETURN

postgresql

plpgsql

database-trigger