如何根据日期删除副本

Question

我有一个表格，其中有几个cust_id重复项。我想保留prendate_next最接近当前日期的行，并删除其余的重复项。请帮帮我。我是这个新手

cust_id     prendate_next
1000105737  2014-11-30 00:00:00.000
1000105836  2014-11-20 00:00:00.000
1000143646  2014-11-10 00:00:00.000
1000143646  2015-03-09 00:00:00.000
1000179487  2014-12-05 00:00:00.000
1000182253  2015-01-01 00:00:00.000
1000192740  2014-10-02 00:00:00.000
1000192740  2015-01-10 00:00:00.000
1000199419  2015-09-30 00:00:00.000
1000170578  2014-12-26 00:00:00.000
1000188890  2015-06-23 00:00:00.000
1000189075  2015-03-01 00:00:00.000
1000189075  2015-03-01 00:00:00.000
1000189144  2015-04-04 00:00:00.000

Answer 1

;WITH cte AS (
    SELECT      cust_id, prendate_next,
                ROW_NUMBER() OVER (PARTITION BY cust_id ORDER BY ABS(DATEDIFF(DAY,prendate_next,GETDATE()))) AS RowNumber
    FROM        MyTable
)

DELETE MyTable
    FROM        MyTable
    INNER JOIN  cte         ON MyTable.cust_id = cte.cust_id
                            AND MyTable.prendate_next = cte.prendate_next
    WHERE       cte.RowNumber != 1

ABS(DATEDIFF(DAY,prendate_next,GETDATE()))计算今天prendate_next的天数。