I do not work in SQL windows. The simple function "between" 10% of the time don't work when importated.

Hi, I am working with 3 acces 2000 database. I have make 20 query to extract informations on these database. The 3 database have the same structure and datatype bot not the same records. When I import my queries to one database to another some of them stop working correctly. For example, if I use the exported query a have approx 8000 records and when I remake the same query (exactly the same) I got a result of 9000 record. Does somebody know why...