加入PSQL三個表（SQL查詢）

Question

我有一個表是這樣的：

UsersDevices: user_id, device_id 
registration_posusercompany: company_id, user_id 
registation_companyprofile: company_id, company_name 

我知道UsersDevices的device_id，我現在想知道該設備所屬的COMPANY_NAME。對於該僞代碼是這樣的：

--> Get user_id from UsersDevices where device_id = (I know this device_id) 
--> Get company_id with that user_id from registration_posusercompany 
--> Get company_name with that company_id 

我寫的子查詢做到這一點，但確實子查詢很慢比較JOIN。我如何使用JOIN實現這一點。謝謝

Answer 1

select rc.company_name 
from UsersDevices as u 
    join registration_posusercompany as rp on rp.user_id = u.user_id 
    join registation_companyprofile as rc on rc.company_id = rp.company_id 
where u.device_id = yourvalue