Crystal Reports 10 - Linking tables through fields with different data types

I am using Crystal Reports 10 with an Access Database. I want to link two tables though fields that have different data types. One is number and other is text.

One way is to have a sub-report. However, that makes the main report run very slow.

I got to know another way is to have add SQL Query to convert data types and link the tables. I am not familiar with SQL. Can anyone please assist.

Thanks