Oracle在3個表格上加入2-3個查找

Question

我不確定我需要什麼類型的JOIN。我有一個表是people。 people表具有id,lastname,firstname,title,departmentid和phone。 第二個表格是department。 department表具有id,name,roomid和telephone。 第三張表是peoplerooms。 peoplerooms只有peopleid和roomid字段。 第四張表是rooms。 rooms具有id,name和roomnumber。

的目標是查詢people和（使用departmentid從department表）返回people.id，lastname，firstname，title，name，也room.name使用peoplerooms找到所有房間的peopleid了。

people table 
- id 
- lastname 
- firstname 
- title 
- departmentid 
- phone 

sample people data 
1|smith|will|director|2|555-555-5555 
2|doe|jane|director|3|555-333-4545 

peoplerooms table 
- peopleid 
- roomid 

sample peoplerooms data 
1|10 
2|5 

rooms table 
- id 
- name 
- roomnumber 

sample rooms data 
3|Room C|100C 
5|Room B|100B 
10|Room A|100A 

department table 
- id 
- name 
- roomid 
- phone 

sample department data 
3|Radiology|5|555-454-4444 
2|Billing|3|656-555-6656 

我有以下SQL工作，但我不是在部門名稱拉......我只得到people.departmentid，我需要查找部門，而是讓department.name。

SELECT people.lastname, people.firstname, people.departmentid, people.title, room.roomnumber, people.phone 
FROM room 
JOIN peopleroom ON room.id = peopleroom.roomid 
JOIN people ON peopleroom.peopleid = people.id 
ORDER BY people.lastname 

Answer 1

你是正確的道路上。請加入department。嘗試以下查詢。我已經添加people.id和room.name，因爲你在你的問題中提到它：

SELECT 
    people.lastname, 
    people.firstname, 
    people.title, 
    people.phone, 

    room.roomnumber, 
    room.name AS roomname, 

    department.name AS departmentname 

FROM 
    room JOIN peopleroom ON room.id = peopleroom.roomid 
    JOIN people ON peopleroom.peopleid = people.id 
    JOIN department ON people.departmentid = department.id 

ORDER BY 
    people.lastname