Every Crystal Report (Selection Criteria) can be rendered into it's constituient "SQL Query".
Note: this will only work on SQL Servers.
Once your report is in place and working as desired, select (from the top-level menu)
Database SQL Query.
You will get a little window that contains the SQL Code used to select the records from the database. You can copy and paste this text into, say, a SQL Query Designer. This is incidentally also a nice way a build SQL Queries using Crystal Reports.