如何獲得通過

Question

聚合組的唯一標識符的主鍵我使用SQL Server 2012的

我有以下表

create table tableA 
(
    ID uniqueidentifier, 
    CustomerId uniqueidentifier, 
    VisitDate DATETIME, 
    [Mark] int 
); 
insert into tableA values 
('80D8F17A-A581-4B62-8245-45276A8422FD','0BD6B2E3-F8DE-463D-8D10-000000D49DC0','2015-09-28 15:23:00.000',100), 
('EBBC88DD-C4F9-480C-9482-5CF72F912237','CE029ECC-0546-4B8B-854B-00000814BB55','2015-09-28 15:10:36.000',200), 
('06A460E4-0702-4872-B3DF-77FF37E9345A','CE029ECC-0546-4B8B-854B-00000814BB55','2015-09-28 15:10:36.000',150), 
('7F2F5C41-E585-454A-B9E1-3DC4DF7D4A04','0BD6B2E3-F8DE-463D-8D10-000000D49DC0','2015-09-29 15:00:00.000',300), 
('0271DD70-422D-4117-8CBE-2C5DA2B84E2C','1E8E91D3-C58C-4C70-86AD-00012C9D5B66','2015-09-30 15:00:00.000',200), 
('91D2BEF4-83EA-4A63-A561-FF32CF6B7C66','1E8E91D3-C58C-4C70-86AD-00012C9D5B66','2015-09-30 16:00:00.000',100), 
('F3C129C7-E4B2-40CA-8A58-973E6AA5D379','1E8E91D3-C58C-4C70-86AD-00012C9D5B66','2015-09-30 17:00:00.000',100), 
('AB20335C-78C6-46A6-88D8-38AC2ED7D023','E60D531F-3F3F-4129-A9AC-00008D20BD36','2015-09-01 12:12:12.000',200); 

我可以得到每個客戶的LastVisitDate像這樣

Select CustomerId,MAX(VisitDate) as lastVisitDate From tableA 
GROUP BY CustomerId 

但是我希望我的輸出只是與我的分組中獲得的上述行對應的主鍵ID。

我該怎麼做？

Answer 1

您可以使用ROW_NUMBER：

WITH CTE AS 
(
    SELECT *, 
      RN = ROW_NUMBER() OVER(PARTITION BY CustomerId 
           ORDER BY VisitDate DESC) 
    FROM tableA 
) 
SELECT ID 
FROM CTE 
WHERE RN = 1;