我需要在postgresql中使用触发器（最好通过SQLALchemy ORM）。然而，我似乎不能得到与创建一个第一基地。作为一个基本测试，我尝试在每次插入行时将字符串“Hello world”放入名为test的列中。
我这样设置我的表：

from __future__ import annotations
from typing import List
import sqlalchemy
from sqlalchemy import create_engine, ForeignKey, Column, Integer, String, CheckConstraint, MetaData
from sqlalchemy.orm import DeclarativeBase, Mapped, DeclarativeBase, MappedAsDataclass, mapped_column, relationship
from sqlalchemy.schema import DDL
import datetime

dbUrl = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

engine = create_engine(dbUrl,
                       echo=True)

metadata = MetaData()


class Base(MappedAsDataclass, DeclarativeBase):
  pass

class Company(Base):
    __tablename__ = "company"
    id: Mapped[int] = mapped_column(primary_key=True)
    name: Mapped[str]
    managers: Mapped[List[Manager]] = relationship(back_populates="company")

Company.__table__
Base.metadata.create_all(engine)

class Employee(Base):
    __tablename__ = "employee"
    id: Mapped[int] = mapped_column(primary_key=True)
    name: Mapped[str]
    type: Mapped[str]
    test: Mapped[str] = mapped_column(nullable=True)

    __mapper_args__ = {
        "polymorphic_identity": "employee",
        "polymorphic_on": "type",
    }

Employee.__table__
Base.metadata.create_all(engine)

class Manager(Employee):
    __tablename__ = "manager"
    id: Mapped[int] = mapped_column(ForeignKey("employee.id"), primary_key=True)
    manager_name: Mapped[str]
    CheckConstraint("manager_name == employee.name", name="check1")

    company_id: Mapped[int] = mapped_column(ForeignKey("company.id"))
    company: Mapped[Company] = relationship(back_populates="managers")

    __mapper_args__ = {
        "polymorphic_identity": "manager",
    }

class Engineer(Employee):
    __tablename__ = "engineer"
    id: Mapped[int] = mapped_column(ForeignKey("employee.id"), primary_key=True)
    engineer_name: Mapped[str]

    company_id: Mapped[int] = mapped_column(ForeignKey("company.id"))
    company: Mapped[Company] = relationship(back_populates="engineers")

    __mapper_args__ = {
        "polymorphic_identity": "engineer",
    }  
Engineer.__table__
Base.metadata.create_all(engine)

字符串
然后尝试创建一个触发器，像这样：

sqlalchemy.event.listen(metadata,
                       "before_create",
                       DDL("""CREATE TRIGGER autoCreateEmployee
                       AFTER INSERT
                       ON employee
                       FOR EACH ROW
                       INSERT INTO employee(test)
                       VALUES("Hello world"),
                       0)  
                       """))

型
创建了表，没有发出任何错误，但据我所知，没有添加触发器。我还尝试使用DBeaver直接在SQL中运行我的测试触发器语句：

CREATE TRIGGER autoCreateEmployee
                       AFTER INSERT
                       ON employee
                       FOR EACH ROW
                       INSERT INTO employee(test)
                       VALUES("Hello world")

型
这给了我这个错误：

SQL Error [42601]: ERROR: syntax error at or near "INSERT"
  Position: 165

Error position: line: 5 pos: 164

型
我的触发器语句有什么问题？为什么我在通过SQLAlchemy运行时看不到错误？
编辑：我试图改编这个例子：

的数据
更新：根据评论，我又看了一下文档，发现我看到的一些例子甚至不是Postgres。现在，我可以运行命令来创建函数和触发器而不会出错，但据我所知，触发器存在（因为我不能在不删除的情况下重新创建它），但似乎与它应该在的表没有关联。
目前我只是运行原始SQL以避免ORM复杂性：

drop function hello_world;

CREATE FUNCTION hello_world() RETURNS trigger AS $hello_world$
    BEGIN
        INSERT INTO employee(test) VALUES ("HELLO WORLD!");
        RETURN NEW;
    END;
$hello_world$ LANGUAGE plpgsql;

drop trigger hello on employee;

CREATE TRIGGER hello
    AFTER UPDATE ON employee
    FOR EACH ROW
    EXECUTE FUNCTION hello_world();

型
编辑2：删除了一个截图，因为它是错误的截图，无论如何都是基于误解。
当前状态：
我的函数是这样的：

CREATE FUNCTION hello_world()
RETURNS trigger
LANGUAGE PLPGSQL
AS $hello_world$
    BEGIN
        INSERT INTO employee(test) VALUES ('HELLO WORLD!');
    END;
$hello_world$

型
我创建触发器如下：

CREATE TRIGGER hello
    AFTER INSERT ON employee
    FOR EACH ROW
    EXECUTE FUNCTION hello_world();

型
但是，它试图在测试列中创建一个仅包含测试字符串的新行，而不是在我刚刚输入数据的行中。我的印象是FOR EACH ROW意味着该函数将在所有插入的行上执行。很明显我还缺少一些东西。
如果我跑：

INSERT INTO employee (name,type) VALUES ('Merv', 'manager');

型
我明白

SQL Error [23502]: ERROR: null value in column "name" of relation "employee" violates not-null constraint
  Detail: Failing row contains (31, null, null, HELLO WORLD!).
  Where: SQL statement "INSERT INTO employee(test) VALUES ('HELLO WORLD!')"
PL/pgSQL function hello_world() line 3 at SQL statement

型
所以现在我需要弄清楚如何使用触发器函数来定位刚刚修改过的行。