Postgresql 為插入/更新中的完整性約束創建觸發器

Question

我在 Postgresql 的數據庫中有這些表：

create table company (
  id bigint generated always as identity primary key,
  name text not null
);

create table employee (
  id bigint generated always as identity primary key,
  name text not null,
  company_id bigint not null references company(id)
);

create table manager_employee(
  id bigint generated always as identity primary key,
  manager_id bigint not null references employee(id),
  employee_id bigint not null references employee(id)
);
create unique index ux1_manager_employee on manager_employee(manager_id, employee_id);
alter table manager_employee add constraint ck1_manager_employee check (manager_id != employee_id);

我想確定當我在manager_employee表中插入/更新一個值時 manager_id 和 employee_id 屬於同一家公司，同一個company_id 。

我想我必須使用觸發器來確保這個條件，我該如何創建它？

謝謝

Answer 1

你可以用約束來做到這一點：

ALTER TABLE manager_employee ADD company_id bigint;

UPDATE manager_employee me
SET company_id = e.company_id
FROM employee e
WHERE me.employee_id = e.id;

ALTER TABLE manager_employee ALTER company_id SET NOT NULL;

ALTER TABLE employee ADD UNIQUE (company_id, id);

ALTER TABLE manager_employee ADD FOREIGN_KEY (company_id, manager_id)
   REFERENCES employee(company_id, id);

ALTER TABLE manager_employee ADD FOREIGN_KEY (company_id, employee_id)
   REFERENCES employee(company_id, id);

唯一約束與新列一樣冗余，但作為外鍵約束的目標是必需的。