Very Computer

I am making query in Access 2000 to FoxPro 2.5 dbf through ODBC and each
time getting
different result.

First query - calls 1:

SELECT DISTINCTROW arsales.invonum, arsales.invoext, arsales.ponum,
arsales.soldto, arsales.billto, arsales.company, arsales.clerk,
arsales.dateord, arsales.dateship, arsales.taxrate, arsales.shipping,
arsales.total, arsales.mkcode, arsales.cod,
(Left([arsales]![mkcode],3)='LLL' Or Left([arsales]![mkcode],3)='CCC' Or
Left([arsales]![mkcode],4)='BBBB') AS Expr1

FROM arsales

WHERE (((arsales.dateship)>=DateValue('05/01/01') And
(arsales.dateship)<=DateValue('08/31/01')) AND
(((Left([arsales]![mkcode],3)='LLL' Or Left([arsales]![mkcode],3)='CCC' Or
Left([arsales]![mkcode],4)='BBBB'))<>False))

ORDER BY arsales.mkcode DESC;

And second one:

SELECT First([calls 1].mkcode) AS FirstOfmkcode, Count(*) AS [Count Of
arsales], Left([arsales]![mkcode],3) AS Expr1

FROM [calls 1]

GROUP BY Left([arsales]![mkcode],3)

ORDER BY Left([arsales]![mkcode],3) DESC;

And result that I got could be:

LLL=21912
CCC=2936
BBBB=218624

Or

LLL=21912
CCC=2937
BBBB=218623

Or

LLL=21911
CCC=2937
BBBB=218624

Always 1 moving to random line!

I checked it through FoxPro and right answer is:

LLL=21912
CCC=2937
BBBB=218623

 Thank you for good explanation

Alex