Question

我正在使用SQL Server 2012而我无法弄清楚如何实现从特定表中的列中提取AVERAGE的代码。如果有人能帮助指出我所附的代码有什么问题，我会感激不尽。

正如您所看到的，我正在加入来自不同表的列以获得我期望的输出。 AVERAGE部分令我头疼！该专栏名为＆＃34; RoomRate＆＃34; （我需要按照ReservationID分组的金额的平均值）和我需要的表格被称为＆＃34; ReservationStayDate＆＃34;。

感谢您的帮助！

USE MY_DATABASE
SELECT a.ReservationStayID,
       a.FirstName + ' ' + a.LastName AS 'Name',
       b.PropertyCode AS'Property',
       b.ReservationStatus,
       b.MarketSegmentCode,
       a.ArrivalDate,
       a.DepartureDate,
       c.AdultCount,
       c.ChildCount,
       b.GuestCount,
       c.TaProfileID,
       c.PMSConfirmationNumber,
       c.CurrencyCode,
       d.rsl_nationality,
       d.rsl_country AS 'Cty of   Residence',
       d.rsl_totalroomrate,
       e.Name AS 'Tour Operator',
       e.CountryCode AS 'Market',
       f.[RateAmount]
FROM GuestNameInfo a
JOIN GuestStaySummary b ON a.ReservationStayID = b.ReservationStayID
JOIN ReservationStay c ON c.ReservationStayID = b.ReservationStayID
JOIN P5RESERVATIONLIST d ON d.rsl_code = b.ReservationStayID
JOIN TravelAgency e ON e.TravelAgencyID = c.TAProfileID
JOIN
  (SELECT avg(RateAmount) AS 'RateAmount'
   FROM ReservationStayDate
   GROUP BY ReservationStayID) ReservationStayDate f ON f.ReservationStayID = a.ReservationStayID

Answer 1

您需要将ReservationStayID放在子选择选择列表中。

如果是一个整数列，也将RateAmount与1.0相乘。

Answer 2

你的sql看起来应该是这样的

USE MY_DATABASE

SELECT a.ReservationStayID,
       a.FirstName + ' ' + a.LastName AS 'Name',
       b.PropertyCode AS'Property',
       b.ReservationStatus,
       b.MarketSegmentCode,
       a.ArrivalDate,
       a.DepartureDate,
       c.AdultCount,
       c.ChildCount,
       b.GuestCount,
       c.TaProfileID,
       c.PMSConfirmationNumber,
       c.CurrencyCode,
       d.rsl_nationality,
       d.rsl_country AS 'Cty of   Residence',
       d.rsl_totalroomrate,
       e.Name AS 'Tour Operator',
       e.CountryCode AS 'Market',
       f.[RateAmount],

 (SELECT avg(RateAmount)
   FROM ReservationStayDate f
   where f.ReservationStayID = a.ReservationStayID ) as RateAmount

FROM GuestNameInfo a
     JOIN GuestStaySummary b ON a.ReservationStayID = b.ReservationStayID
     JOIN ReservationStay c ON c.ReservationStayID = b.ReservationStayID
     JOIN P5RESERVATIONLIST d ON d.rsl_code = b.ReservationStayID
     JOIN TravelAgency e ON e.TravelAgencyID = c.TAProfileID

Answer 3

使用OVER子句，因为它比使用子查询派生聚合值更有效。

USE MY_DATABASE
SELECT a.ReservationStayID,
       a.FirstName + ' ' + a.LastName AS 'Name',
       b.PropertyCode AS'Property',
       b.ReservationStatus,
       b.MarketSegmentCode,
       a.ArrivalDate,
       a.DepartureDate,
       c.AdultCount,
       c.ChildCount,
       b.GuestCount,
       c.TaProfileID,
       c.PMSConfirmationNumber,
       c.CurrencyCode,
       d.rsl_nationality,
       d.rsl_country AS 'Cty of   Residence',
       d.rsl_totalroomrate,
       e.Name AS 'Tour Operator',
       e.CountryCode AS 'Market',
       --Aggregate function with Over clause
       AVG(f.RateAmount) OVER(PARTITION BY a.ReservationStayID) AS RateAmount
FROM GuestNameInfo a
JOIN GuestStaySummary b ON a.ReservationStayID = b.ReservationStayID
JOIN ReservationStay c ON c.ReservationStayID = b.ReservationStayID
JOIN P5RESERVATIONLIST d ON d.rsl_code = b.ReservationStayID
JOIN TravelAgency e ON e.TravelAgencyID = c.TAProfileID
JOIN ReservationStayDate f ON f.ReservationStayID = a.ReservationStayID

在SQL Query中使用Average函数和JOIN函数

3 个答案: