Question 70
A many-to-many relationship appears after data loading because a supposed customer lookup repeats keys. What is the most direct diagnostic?
Explanation
Correct Answer
Profile the lookup's key cardinality and repair or remodel its duplicates. Key duplication can force unexpected relationship cardinality.
Incorrect Answers
Repeated invoice numbers do not imply duplicate transaction lines. The boundary it addresses is “and a developer deletes duplicates on invoice number”, while this case concerns “loading because a supposed customer lookup repeats keys”.
Test CustomerID uniqueness before defining the one-side relationship. This solves “rows and must be one row per key”; the stated issue is “loading because a supposed customer lookup repeats keys”.
Latest-version selection needs a stable tie-break rather than arbitrary duplicate removal. The deciding difference is “versions for each customer with a LastUpdated timestamp” versus “loading because a supposed customer lookup repeats keys”.