A business analyst is using a client table and an invoice table to create a database view that shows clients who have not made purchases yet. Which of the following joins is most appropriate for the…

The correct answer is D. LEFT JOIN ON Client.Key = Invoice.Key WHERE BY Invoice.Key IS NULL. To find clients with no purchases, you need a LEFT JOIN from the Client table to the Invoice table, then filter WHERE Invoice.Key IS NULL. The LEFT JOIN returns all rows from Client regardless of whether a matching invoice exists - unmatched clients will have NULL in all…

Database Fundamentals

Question

A business analyst is using a client table and an invoice table to create a database view that shows clients who have not made purchases yet. Which of the following joins is most appropriate for the analyst to use to create this database view?

Options

AINNER JOIN ON Client.Key = Invoice.Key
BRIGHT JOIN ON Client.Key = Invoice.Key WHERE BY Client.Key IS NULL
CLEFT JOIN ON Client.Key = Invoice.Key
DLEFT JOIN ON Client.Key = Invoice.Key WHERE BY Invoice.Key IS NULL

How the community answered

(34 responses)

A
12% (4)
B
3% (1)
C
3% (1)
D
82% (28)

Explanation

To find clients with no purchases, you need a LEFT JOIN from the Client table to the Invoice table, then filter WHERE Invoice.Key IS NULL. The LEFT JOIN returns all rows from Client regardless of whether a matching invoice exists - unmatched clients will have NULL in all Invoice columns. The WHERE Invoice.Key IS NULL clause then filters to show only those unmatched clients (i.e., clients who have never made a purchase). Choice C (LEFT JOIN without the WHERE clause) returns all clients including those who have made purchases. Choice A (INNER JOIN) returns only clients who DO have invoices - the opposite of what is needed. Choice B uses a RIGHT JOIN with the wrong NULL check.

Topics

#SQL Joins#Outer Joins#Data Retrieval#NULL Values

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