Try this (you will probably need to modify it for your own use).

SELECT *, [keyinfo], count(*) as nTotal FROM yourtable GROUP BY [keyinfo] HAVING nTotal>1

The HAVING may need to use count(*) instead of nTotal (I can't remember) but this will give you a list of duplicate entries.

>Hi everybody,
>
> I have a problem, which seems to me quite complicated. I need to find possible dupes in my table by address information and the date (date of transaction) should be in the particular range od days, say, within one week.
>
> As I can judge, it could not be done in one query...
>
> Could you please advise me more efficient way to find these possible dupes?
>
> The number of dupes may vary (in most cases, 2, but could be 3,4 or more).
>
> Thanks in advance.