在相同和不同表中针对不同ID的多个联接

Question

I've different tables and I've to fetch data.

order table

orderId, clientId, buyerId, loadingCompanyId, productTypeId, orderStatusId

user table

userId, userCompanyName

orderStatus table

orderStatusId, orderStatusName,

productType table

productTypeId, productTypeName

so I've these tables. In order table clientId, buyerId and loadingCompanyId are coming from user's table userId and I want to fetch its userCompanyName, orderStatusId is coming from orderStatus table and I want to fetch orderStatusName and last one is productTypeName productTypeId is coming from productType table and want to fetch productTypeName but the problem is with clientId, buyerId and loadingCompanyId these three ids are userId from user table so how I've to fetch client, buyer and loading company names.

Answer 1

That are some simple joins with aliases

select * 
from order 
join user client on clientId = client.userId
join user buyer on buyerId = buyer.userId
join user company on loadingCompanyId = company.userId
join orderStatus  on orderStatus.orderStatusId= order.orderStatusId
join productType on productType.productTypeId = order.productTypeId

Answer 2

SELECT O.orderId, UserClient.userCompanyName As clientName, UserBuyer.userCompanyName AS buyerName, UserloadingCompany.userCompanyName AS buyerName, OS.orderStatusName, PT.productTypeName
FROM Order O
INNER JOIN user AS UserClient
ON O.clientId = UserClient.userId
INNER JOIN user AS UserBuyer
ON O.buyerId = UserBuyer.userId
INNER JOIN user AS UserloadingCompany
ON O.loadingCompanyId = UserloadingCompany.userId
INNER JOIN orderStatus AS OS
ON O.orderStatusId = OS.orderStatusId
INNER JOIN productType AS PT
ON O.productTypeId = PT.productTypeId