Tables never join automatically. Do you mean preventing association? That can only be done by renaming fields. That's because the only way to associate tables is to give the fields that should be used for the associated the same name. You can use the QUALIFY keyword to prefix all the fields with the table name. That will make the field names unique and will prevent any associations. It will result in data island tables which are likely to cause horribly bad performance and hard to predict results.
thx for you reply. The QUALIFY function was exaclty what I was looking for and yes I did indeed mean association (I renamed this discussion). I dont want many separate tables and therefore data islands but I want to control the associated fields of the tables. I my case I got many data sources with identical field names and I didnt wanted to rename them all manually.
Thy for your help, I really appreciate it.