From what DBlank posted about the enforce, you wouldn't see a difference. Regardless of enforce, there would only be 1 column...the question is if it would be null...but the sql statement is an inner join, just read it, it is old syntax, implicit inner join.
Again, referring to the posting, it would appear that ENFORCE is a method for CRYSTAL to not process/retrieve information that is not used in the report. When you join 2 tables with 100 columns each, but then don't reference any of the columns in one of the tables, this would allow Crystal to not retrieve the data from the unused table...regardless of join type. (this is my interpretation of what the help says)...
My recommendation, forget about Enforce, just use the normal SQL joins that are well documented all over the web and are easily understood.
And as always, get your data from a stored proc or a view...then this whole issue is gone and you are maximizing the processing power of your database software and server hardware, which is why you bought it.