SQL查詢優化/重構

Question

只是想知道任何人都可以看到一種更簡潔的方式來編寫這個查詢。 對我來說似乎有很多重復，但我看不出更簡單的方法來寫它。 它正在拉回年初至今的數據。

輸出如下：

name  Total New Drives  Total New Sales  Total Used Drives Total Used Sales    
Alan    41                31                 15               93    
Pascal  45                51                 35               33   

查詢是：

select sp.name, x.ttlNewTestDrives, x.ttlNewSales, y.ttlUsedTestDrives, y.TtlUsedSales
from
(
    select ts.SalesPersonID, ttd.TotalTestDrives as TtlNewTestDrives ,ts.TotalSales as TtlNewSales
    from
    (       
            select  sp.[SalesPersonID], count([TestDriveID]) as TotalTestDrives
            from SalesPeople sp
            join TestDrives td 
            on sp.[SalesPersonID] = td.[SalesPerson_SalesPersonID]
            join cars c on
            c.[CarID] = td.[Car_CarID]
            where c.CarType = 'New'
            group by sp.[SalesPersonID]
        ) as ttd
    full outer join
        (
            select sp.[SalesPersonID], count(SaleID) as TotalSales
            from Sales s
            join SalesPeople sp
            on s.[Salesperson_SalesPersonID] = sp.[SalesPersonID]
            join cars c on
            s.[Car_CarID] = c.[CarID]
            where c.CarType = 'New'
            group by sp.[SalesPersonID]
        ) as ts
    on ts.[SalesPersonID] = ttd.[SalesPersonID]
    ) as x
full outer join
(   
        select ttd.SalesPersonID, ttd.TotalTestDrives as TtlUsedTestDrives ,ts.TotalSales as TtlUsedSales
        from
        (       
                select  sp.[SalesPersonID], count([TestDriveID]) as TotalTestDrives
                from SalesPeople sp
                join TestDrives td 
                on sp.[SalesPersonID] = td.[SalesPerson_SalesPersonID]
                join cars c on
                c.[CarID] = td.[Car_CarID]
                where c.CarType = 'Used'
                group by sp.[SalesPersonID]
            ) as ttd
        full outer join
            (
                select sp.[SalesPersonID], count(SaleID) as TotalSales
                from Sales s
                join SalesPeople sp
                on s.[Salesperson_SalesPersonID] = sp.[SalesPersonID]
                join cars c on
                s.[Car_CarID] = c.[CarID]
                where c.CarType = 'Used'
                group by sp.[SalesPersonID]
            ) as ts
        on ts.[SalesPersonID] = ttd.[SalesPersonID]
    ) y
on x.[SalesPersonID] = y.[SalesPersonID]
join SalesPeople sp
on x.[SalesPersonID] = sp.[SalesPersonID]

Answer 1

您當然可以使用以下內容減少查詢中的代碼量：

select sp.name, td.NewTestDrives, s.NewSales, td.UsedTestDrives, s.NewSales
from SalesPeople sp
  left join
  (
    select td.[SalesPerson_SalesPersonID]
      , NewTestDrives = sum(case when c.CarType = 'New' then 1 else 0 end)
      , UsedTestDrives = sum(case when c.CarType = 'Used' then 1 else 0 end)
    from TestDrives td 
      inner join cars c on c.[CarID] = td.[Car_CarID]
  ) td on sp.SalesPersonID = td.[SalesPerson_SalesPersonID]
  left join
  (
    select s.[SalesPerson_SalesPersonID]
      , NewSales = sum(case when c.CarType = 'New' then 1 else 0 end)
      , UsedSales = sum(case when c.CarType = 'Used' then 1 else 0 end)
    from Sales s 
      inner join cars c on c.[CarID] = s.[Car_CarID]
  ) s on sp.SalesPersonID = s.[SalesPerson_SalesPersonID]

我已經淘汰了很多重復的連接，並從完全連接移動到左邊將兩個匯總結果集（測試驅動器和銷售）連接到銷售人員表。

您沒有提供表格或任何示例數據的詳細信息，因此無法測試上述查詢，但希望它能為您提供有關如何更簡潔地編寫它的一些想法。

就實際性能而言，我認為簡化代碼可能會有助於優化器，但這是您需要在自己的環境中確認的。