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 12/29/11 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

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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.[Date] >= wwk.StartDate AND w.[Date] <= 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!