更新重複記錄，保留記錄（Min）（日期）相同

Question

這是我的問題;

我運行此查詢，並得到那些擁有「FirstTimeBooking」 = 1多行13469個用戶：

Select CustUserId, COUNT(CustUserId) 
FROM Bookings with (nolock) 
WHERE FirstTimeBooking = 1 
GROUP BY CustUserId 
HAVING COUNT(CustUserId) > 1 
ORDER BY COUNT(CustUserId) DESC 

我需要更新所有的這些記錄，對於每一行設置FirstTimeBooking = 0，除了閔（ BookingDate）爲每個用戶（這是實際的FirstTimeBooking）。任何幫助將不勝感激。

Answer 1

我試圖保持它的簡單，並留在你的語法：

CREATE TABLE Bookings 
(
CustUserID int 
,FirstTimeBooking int 
,BookingDate datetime 
) 

INSERT INTO Bookings VALUES 
(1, 1, '20170101') 
,(1, 1, '20170101') -- Duplicate on same date 
,(2, 1, '20170201') 
,(2, 1, '20170301') -- On a second date 
,(3, 1, '20170401') 

UPDATE a 
SET FirstTimeBooking = 0 
FROM Bookings as a 
LEFT OUTER JOIN (
    -- Only CustUserID 1 and 2 
    SELECT CustUserID, min(BookingDate) as BookingDate 
    FROM Bookings 
    WHERE FirstTimeBooking = 1 
    GROUP BY CustUserID 
    HAVING COUNT(*) > 1 
) as b 
on a.CustUserID = b.CustUserID 
and a.BookingDate = b.BookingDate 
WHERE b.BookingDate IS NULL -- only where the first booking date has not been found in subquery 

-- Still got the Problem with CustUserID 
SELECT * 
FROM Bookings 
WHERE CustUserID = 1 

UPDATE b 
set FirstTimeBooking = 0 
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY CustUserID ORDER BY CustUserID) As Rown 
FROM Bookings as b 
WHERE FirstTimeBooking = 1 
) as b 
WHERE Rown = 2 

-- This is now also solved 
SELECT * 
FROM Bookings 
WHERE CustUserID = 1 

也許你沒有兩個完全相同的BookingDates，但我加入這個以防萬一。

Regards tgr