Joining records.
WHEN THIS ARISES
Sales in one system, customers in another Costs in accounting, jobs in a spreadsheet Website enquiries and actual sales
WHAT IS REQUIRED
A common identifier in both.
WHAT SERVES AS ONE
A customer reference An invoice number An order number An email address, imperfectly
THE EMAIL ADDRESS PROBLEM
People use several, and they change.
Workable and unreliable.
WHAT TO DO
Establish a customer reference and use it everywhere.
WHAT GOES WRONG WHEN JOINING
Records matching nothing Records matching several Duplicates created by the join
WHAT TO CHECK AFTER COMBINING
Whether totals match the source How many records failed to match
THAT SECOND CHECK
The one people skip, and the one that reveals the problem.
WHAT TO DO WITH UNMATCHED RECORDS
Investigate. They frequently indicate a data quality issue.
WHAT TO AVOID
Combining and analysing without verifying the join.
