Table joins

I'm writing a watch-dog report that looks for Jobs with
JobHead.StartDates after (later than)OrderDtl.NeedByDates. I've tried
various table joins of JobHead, JobProd, and OrderDtl but can't find
one that won't duplicate lines, i.e., it grabs lines that don't

For example, my report might have 9 lines with the same Partnum but
only 3 are correct and I can't tell which ones. Can somebody help?

Thank you in advance.
Steve Shapiro