组不在SQL Server中工作

Question

CREATE VIEW [dbo].[Payment_Transaction_vw]
AS 
SELECT payment_trans_id,
       Student_Info.student_fname,
       Student_Info.student_lname,
       Student_Info.ID_Number,
       Trimester_Payment.deadline,
       Transaction_Info.trans_name,
       Payment_Transaction.amount,
       Payment_Transaction.date_paid
FROM [Payment_Transaction]
  INNER JOIN Student_Info 
    ON Payment_Transaction.student_info_id = Student_Info.student_info_id
  INNER JOIN Trimester_Payment 
    ON Payment_Transaction.trimester_id = Trimester_Payment.trimester_id
  INNER JOIN Transaction_Info 
    ON Payment_Transaction.trans_info_id = Transaction_Info.trans_info_id
GROUP BY ID_Number,trans_name;

这是我在Visual Studio的sql server中创建视图的脚本，我想将ID_Number＆amp; trans_name在表Payment_Transactions中具有重复值。我希望这个带有trans_name的ID_Number只显示一次。我还想总结每个具有相同trans_name的ID_number所支付的金额。

Answer 1

您必须聚合不在group by子句中的列。

例如，您想要返回date_paid（payment_trans_id = 1和2）中的哪一个？ 2015年6月25日或2015年5月6日？ SQL服务器不知道，所以你得到多行。

Answer 2

使用group by时，您需要确保聚合或合并任何唯一值，以便可以在一行中显示。就像现在一样，payment_trans_id（和其他人）仍然是唯一的，因为你选择显示这些组是不可能完成的。

您想对payment_trans_id，date_paid，amount ...所有其他专栏做什么？

使用MAX()，MIN()和AVG()的示例：

SELECT 
  MAX(payment_trans_id) AS payment_trans_id,
  Transaction_Info.trans_name,
  Student_Info.ID_Number, 
  AVG(Payment_Transaction.amount) AS amount,
  MIN(Payment_Transaction.date_paid) AS date_paid
FROM [Payment_Transaction]
INNER JOIN Student_Info ON Payment_Transaction.student_info_id = Student_Info.student_info_id 
INNER JOIN Trimester_Payment ON Payment_Transaction.trimester_id = Trimester_Payment.trimester_id 
INNER JOIN Transaction_Info ON Payment_Transaction.trans_info_id = Transaction_Info.trans_info_id 
GROUP BY ID_Number, trans_name;

对于EF的支持，也许这就足够了（也许不是）：

SELECT 
  ISNULL(MAX(payment_trans_id),0) AS Id,
  Transaction_Info.trans_name,
  Student_Info.ID_Number, 
  AVG(Payment_Transaction.amount) AS amount,
  MIN(Payment_Transaction.date_paid) AS date_paid
FROM [Payment_Transaction]
INNER JOIN Student_Info ON Payment_Transaction.student_info_id = Student_Info.student_info_id 
INNER JOIN Trimester_Payment ON Payment_Transaction.trimester_id = Trimester_Payment.trimester_id 
INNER JOIN Transaction_Info ON Payment_Transaction.trans_info_id = Transaction_Info.trans_info_id 
GROUP BY ID_Number, trans_name;