如何使用聚合T-SQL獲取日期？

Question

我正在嘗試獲取客戶的總訪問次數，並獲取上次訪問日期和nextVisited

SELECT 
  COUNT( VisitTracking.customerID) AS #VISIT, 
  Customers.title, 
  Customers.firstName, 
  Customers.LastName, 
  Company.companyName, 
  VisitTracking.DateVisited, 
  CONVERT(date,VisitTracking.nextVisit)AS nextVisit
FROM VisitTracking 
  INNER JOIN Customers ON VisitTracking.customerID = Customers.customerID 
  INNER JOIN Customer_Company ON Customers.customerID = Customer_Company.customerID 
  INNER JOIN Company ON Customer_Company.companyID = Company.companyID
GROUP BY 
  Customers.title, 
  Customers.firstName, 
  Customers.LastName, 
  Company.companyName,
  VisitTracking.DateVisited,
  VisitTracking.nextVisit

結果

#VISIT, title, firstName ,LastName, companyName, DateVisited, nextVisit
1,        Mr, Tom, Tom, Jedii design, 2012-11-09, 2012-11-14
2 ,       Mr, Sam, Tom, compudata, 2012-11-10, 2012-11-14
1,       Mr, Mike, Mike, compudata, 2012-11-10, 2012-11-14
1,       Mr, Mike, Mike, compudata, 2012-11-16 ,2012-11-23
1,       Mr, Ryan, Ryan, compudata, 2012-11-07 ,2012-11-09

Answer 1

SELECT 
  COUNT( VisitTracking.customerID) AS #VISIT, 
  Customers.title, 
  Customers.firstName, 
  Customers.LastName, 
  Company.companyName, 
  max(VisitTracking.DateVisited) as lastVisit, 
  max(CONVERT(date,VisitTracking.nextVisit)) AS nextVisit
FROM VisitTracking 
  INNER JOIN Customers ON VisitTracking.customerID = Customers.customerID 
  INNER JOIN Customer_Company ON Customers.customerID = Customer_Company.customerID 
  INNER JOIN Company ON Customer_Company.companyID = Company.companyID
GROUP BY 
  Customers.title, 
  Customers.firstName, 
  Customers.LastName, 
  Company.companyName