> Yes, I meant - my table has an adrress information (ccode+town+street+stnum+stnumext), which should be the same for dupes, and a date of transaction (field date), which for possible duplicates may vary in a particular range, specified by user. By default it's 7 day range.
>
> So, I may try something like:
> SELECT *, recno()...
I don't know why you need recno(), though it could come in handy for a related problem other than this one. It's good for offset self-joins, which you could use, for example, to return the number of days for each pair. But anyway...

...FROM mytable INNER JOIN mytable AS my ON mytable.pk=my.pk and mytable.address = my.address...

You don't need these in the join expression. The point is to join records with different keys on close dates:

...and between(mytable.date, my.date-7, my.date+7)

You might not need -7 and +7. Either one should find all the matches. I suppose that 7 will be replaced by a variable holding the user-selected value.

The refinements depend on the purpose of the query and definition of the problem. This query should match each record to every other record with a nearby date: if you have three records with datefields {^2000/04/05}, {^2000/04/07}, and {^2000/04/08} the first will join to the second and third, and the second will join to the third. If you use -7 and +7, each record will join to each of the others.

If you only want to join {^2000/04/05} with {^2000/04/07} and {^2000/04/07} with {^2000/04/08} and not join {^2000/04/05} with {^2000/04/08} you would use what I call an offset self-join. You would do something like this:

SELECT * FROM mytable INTO CURSOR mysorted ORDER BY mydate
SELECT *, RECNO() AS numrec FROM mysorted INTO CURSOR mynumbered
SELECT mysorted.whatever, mysorted.mydate - my2.mydate AS datediff FROM mysorted INNER JOIN mysorted AS my2 ON mysorted.numrec = my2.numrec - 1 WHERE mysorted.mydate >= my2.mydate - 7

You don't need "mysorted.mydate - my2.mydate AS datediff" in there but it might come in handy for something. All +, -, <, and > may require reversing in my examples - I often get those wrong.

>>if you have records for eight consecutive days? How many dupes is that? A SQL solution might involve some sort of non-equi-self-join, something like
>>
>>SELECT * FROM yourtable INNER JOIN yourtable AS yours1 ON yourtable.yourdate <= yours1.yourdate - 7
>>