ExpertHard1 markMultiple Choice
CPA · Question 20 · Area I: Information Systems
Which of the following SQL statements would be most useful for an auditor attempting to identify duplicate invoice numbers in a table named 'Invoices'?
Which of the following SQL statements would be most useful for an auditor attempting to identify duplicate invoice numbers in a table named 'Invoices'?
Answer options:
A.
SELECT DISTINCT InvoiceNum FROM Invoices
B.
SELECT * FROM Invoices ORDER BY InvoiceNum
C.
SELECT InvoiceNum, COUNT() FROM Invoices GROUP BY InvoiceNum HAVING COUNT() > 1
D.
SELECT InvoiceNum FROM Invoices WHERE InvoiceNum IS NOT NULL
How to approach this question
To find duplicates, you need to count occurrences of each item and look for counts > 1. This requires GROUP BY and HAVING.
Full Answer
C.SELECT InvoiceNum, COUNT(*) FROM Invoices GROUP BY InvoiceNum HAVING COUNT(*) > 1✓ Correct
The GROUP BY clause groups rows with the same values, and HAVING COUNT(*) > 1 filters those groups to show only the ones that appear multiple times (duplicates).
Common mistakes
Using DISTINCT (which removes duplicates) instead of finding them.
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