Imagine this scenario: You're the DBA for your company's transactional production database, and you're preparing to extract data from the database so that you can create a report for one of your company's project managers. However, you can't decide whether you should use the data from table PMBPMSRC or from table PMBPMSTRT because they contain the same two fields: OBJT and STRN. When you ask the manager who requisitioned the report which table to use, she doesn't know, either. But in the end, kn...