Question

我有这两个表：

表1：客户名称BillDate

CITY - BEAUTIFICATION LM            2013-05-30 00:00:00.000
CITY - BEAUTIFICATION LM            2013-06-28 00:00:00.000
CITY - PARKS/RT 66                  2012-07-12 00:00:00.000
CITY - PARKS/RT 66                  2012-07-12 00:00:00.000

依旧......

Table2的字段为：CycleStartDate

我想将Table1中的数据插入到Table2中，如下所示：对于每个唯一的customerName，CycleStartDate是前一记录中的BillDate。如果先前的记录不存在，请将NULL替换为2013-07-1 00：00：00.000。

我们可以做那样的事吗？

Answer 1

嗯，这是假设SQL Server 2005 +的一种方式：

;WITH CTE AS
(
    SELECT  CustomerName,
            BillDate,
            RN1=ROW_NUMBER() OVER(PARTITION BY CustomerName ORDER BY BillDate),
            RN2=ROW_NUMBER() OVER(PARTITION BY CustomerName ORDER BY BillDate DESC)
    FROM dbo.Table1
)
INSERT INTO dbo.Table2(CustomerName, CycleStartDate)
SELECT  CustomerName,
        CASE WHEN RN2 = 1 THEN '20130701' ELSE CycleStartDate END
FROM CTE
WHERE RN1 = 1

Answer 2

如果SQL Server少于2012，请尝试使用

select T.CustomerName, isnull(TP.BillDate, '20130701') as CycleStartDate
from Table1 as T
   outer apply (
       select top 1 T2.BillDate
       from Table1 as T2
       where T2.CustomerName = T.CustomerName and T2.BillDate < T.BillDate
       order by T2.BillDate desc
   ) as TP

如果您有SQL Server 2012，请参阅LAG()功能

SQL Server将以前的值插入新列

2 个答案: