原作者：Juan Soto 翻译：周芳    

     一天,我叫Ben帮我解决一个棘手的问题,我需要将一个表中的记录和另一个有日期范围的表相匹配。这是我要更新的表,表名为tblWidgets.

 WidgetID DateProduced    WidgetWeekID
-------  ------------    ------------
1           1/2/11
2           1/16/11
3           1/31/11

WidgetWeekID是另一个表名为tblWidgetWeeks中的字段:

WidgetWeekID     StartDate    EndDate
------------     --------     -------
 1                12/29/10    1/5/11
 2                1/6/11      1/12/11
 3                1/13/11     1/20/11
 4                1/21/11     1/28/11
 5                1/29/11      2/5/11

    我需要一个查询来找到StartDate和EndDate之间的DateProduced ，然后用正确的编号更新WidgetWeekID。这是他想出的解决方案：

Update tblWidgets AS w
INNER JOIN tblWidgetWeeks AS wwk
  ON w.[DateProduced] >= wwk.StartDate AND w.[DateProduced ] <= wwk.EndDate
 SET w.WidgetWeekID = [wwk].[WidgetWeekID];

     Ben用连接日期范围来解决的方法出色在哪呢,其实它是一个远比使用代码更好的解决办法。运行查询后显示是这样的：

WidgetID DateProduced   WidgetWeekID
-------  ------------   ------------
1          1/2/11            1
2          1/16/11           3
3          1/31/11           5

你还有什么其他不寻常的想法可以加入吗?下面请赐教。谢谢Ben。

另附示例：

点击下载此附件

【原文】
Matching records using a date range

The other day I asked Ben to help me with a thorny problem, I needed to match records in one table with records in another table using a date range. Here’s the table I needed to update, called tblWidgets:

WidgetID DateProduced   WidgetWeekID
-------  ------------   -----------
1           1/2/11
2           1/16/11
3           1/31/11

WidgetWeekID comes from another table called tblWidgetWeeks:

WidgetWeekID      StartDate    EndDate
 ------------     --------     -------
 1                12/29/10     1/5/11
 2                1/6/11       1/12/11
 3                1/13/11      1/20/11
 4                1/21/11      1/28/11
 5                1/29/11       2/5/11

I needed a query that would find DateProduced between StartDate and EndDate and update WidgetWeekID with the right number. Here’s the solution he came up with:

Update tblWidgets AS w
INNER JOIN tblWidgetWeeks AS wwk
  ON w.[DateProduced] >= wwk.StartDate AND w.[DateProduced ] <= wwk.EndDate
 SET w.WidgetWeekID = [wwk].[WidgetWeekID];

What's brilliant about Ben's solution is the join on the date range, a far better solution than using code. Once I ran the query the destination table looks like this:

WidgetID    DateProduced   WidgetWeekID
-------     ------------   ------------
1              1/2/11           1
2              1/16/11          3
3              1/31/11          5

What other unusual joins have you done? Please comment below. Thanks Ben!

相关类似示例:

数据字段值区间转换示例