PostgreSQL內部連接和左連接

Question

我使用postgres 9.5具有以下數據庫結構：

create table users (
  id character varying(255), 
  email character varying(127)
);

create table org_users(
  id character varying(255), 
  user_id character varying(255), -- foreign key to users.id
  manager_org_user_id character varying(255) -- refers to org_users.id; same table referential dependency
);

insert into users (id, email) values ('111', 'user1@example.com');
insert into users (id, email) values ('222', 'user2@example.com');
insert into users (id, email) values ('333', 'manager@example.com');

insert into org_users (id, user_id, manager_org_user_id) values ('o1', '111', 'o3');
insert into org_users (id, user_id, manager_org_user_id) values ('o2', '222', 'o3');
insert into org_users (id, user_id, manager_org_user_id) values ('o3', '333', null);

我的桌子上有三個用戶。 user1@example.com和user2@example.com是兩個普通用戶。 manager@example.com是他們的經理。 現在，我要顯示以下結構：

org_user_id, employee_user_id, employee_email, manager_org_user_id, manager_user_id, manager_email

我嘗試使用以下sql查詢，但由於syntax error near JOIN而無法為我工作。 有什么幫助嗎？

select ou.id as employee_org_user_id,
    us.id as employee_user_id, 
    us.email as employee_email, 
    ou.manager_org_user_id as manager_org_user_id,
    u2.email as manager_email
from org_users ou 
    JOIN users us ON ou.user_id::text = us.id::text,
    LEFT JOIN org_users ou1 ON ou1.id::text = ou.manager_org_user_id::text
    LEFT JOIN users us2 ON ou1.user_id::text = us2.id::text;

Answer 1

刪除空間，重命名u2.email，將演員表放到文本上：

select ou.id as employee_org_user_id,
    us.id as employee_user_id, 
    us.email as employee_email, 
    ou.manager_org_user_id as manager_org_user_id,
    us2.email as manager_email
from org_users ou 
    JOIN users us ON ou.user_id = us.id
    LEFT JOIN org_users ou1 ON ou1.id = ou.manager_org_user_id
    LEFT JOIN users us2 ON ou1.user_id = us2.id

Answer 2

此查詢解決了您的問題：

SELECT ou.id as employee_org_user_id,
       us.id as employee_user_id, 
       us.email as employee_email, 
       ou.manager_org_user_id as manager_org_user_id
FROM org_users ou JOIN users us ON ou.user_id = us.id

---

現場示例：

• http://tpcg.io/PuMym5