SQL Server：查詢聯接多個表和分組依據

Question

我想加入以下三個SQL Server表，如圖所示。 我知道他們必須JOIN ，但我認為正是GROUP BY令我失望。 我認為這需要在SELECT內進行SELECT ？

select ActJobs.ID as JobID, ActJobs.JobName, ActJobs.CustomerID
From Job.ActiveJobsTbl as ActJobs

select Cus.ID as CustomerID, concat(Cus.LastName, ', ', Cus.FirstName) as Customer
From Customer.CustomerTbl as Cus

Select Est.ID_Job as JobID, Sum(Est.ItemAmount + Est.SalesTax) As Price
From Job.EstimateTbl as Est 
Group By Est.ID_Job

Answer 1

您可以簡單地JOIN前兩個表，然后將聚合查詢轉換為可以JOIN的子查詢：

SELECT 
    ActJobs.ID as JobID, 
    ActJobs.JobName, 
    ActJobs.CustomerID,
    CONCAT(Cus.LastName, ', ', Cus.FirstName) as Customer,
    Est.Price
FROM 
    Job.ActiveJobsTbl AS ActJobs
    INNER JOIN Customer.CustomerTbl AS Cus ON Cus.ID = ActJobs.CustomerID
    INNER JOIN (
        SELECT ID_Job, SUM(ItemAmount + SalesTax) As Price 
        FROM Job.EstimateTbl
        GROUP BY ID_Job
    ) AS Est ON Est.ID_Job = ActJobs.ID

Answer 2

使用標量子查詢並加入

select ActJobs.ID as JobID, ActJobs.JobName, ActJobs.CustomerID,
concat(Cus.LastName,', ',Cus.FirstName) as Customer,(select Sum(Est.ItemAmount + Est.SalesTax) from Job.EstimateTbl as Est where Est.ID_Job=ActJobs.ID) as price
From Job.ActiveJobsTbl as ActJobs
inner join Customer.CustomerTbl as Cus on Cus.ID as CustomerID=ActJobs.CustomerID