Introduction: "We just want a list of their email addresses"

This problem is inspired by an actual situation at the Yukon Government: They wanted to send an email to every employee, and that wasn't as easy as you migh expect. The problem is that they can't easily generate a list of all their employees with their email addresses (or at least they couldn't a couple of years ago). The problem is that the employee name and id number is kept in one database system (PeopleSoft), while their email addresses and network logins are maintained in another (an Active Directory repository). Having two database systems is not necessarily a problem, but in this case it is because the two databases do not have a shared field. This makes it difficult to combine them and generate a list of employee names and email addresses. (In relational database terms we would like to do a join on the two tables, but can't because they do not have a shared field, specifically one that is a primary key field in one table and a foreign key field in the other. There's your jargon for the day.)

We can extract records like this from PeopleSoft,

and ones like this from Active Directory,

but we want to generate ones like this that combine a field from each table.

Do you see a pattern? Doesn't it make you want to automate the solution to this problem?