Databricks Data Engineer Associate Question 184: You are working with two datasets in Databricks: orders and customers.... | Databricks Data Engineer Associate Dumps

Databricks Certified Data Engineer Associate. Associate level, Databricks. Free question with the correct answer and a full explanation.

Databricks Data Engineer Associate Question 184

Select 2

You are working with two datasets in Databricks: orders and customers. The orders dataset has columns order_id, customer_id, and amount, while the customers dataset has columns customer_id and customer_name. You execute the following query to join these datasets:

SELECT o.order_id, o.amount, c.customer_name FROM orders o LEFT JOIN customers c ON o.customer_id = c.customer_id;

Which result will be returned by this query?

A
All rows from the orders table with matching rows from the customers table. If no match is found, customer_name will be NULL.
B
Only rows from the orders table where there is a matching customer_id in the customers table.
C
All rows from the customers table with matching rows from the orders table. If no match is found, order_id and amount will be NULL.
D
The result will include rows where customer_id exists in both orders and customers, and rows from orders with NULL values for customer_name if no match is found in customers.
E
Rows where customer_id exists only in the customers table will be included in the result, even if they have no matching rows in the orders table.

Show answer and explanation

Correct answers: A, D

Explanation

A LEFT JOIN in SQL returns all rows from the left table (in this case, orders), and the matching rows from the right table (customers). If there is no match, the result will include NULL values for columns from the right table. This ensures that no rows are excluded from the orders table, even if there is no corresponding record in the customers table.

A. Correct.
Correct: This is the expected behavior of a LEFT JOIN. All rows from the orders table will be included, and if there is no matching customer_id in the customers table, the customer_name column will have NULL values.
B. Incorrect.
Incorrect: This describes the behavior of an INNER JOIN, not a LEFT JOIN.
C. Incorrect.
Incorrect: This describes the behavior of a RIGHT JOIN, not a LEFT JOIN. A LEFT JOIN prioritizes the left table (orders in this case).
D. Correct.
Correct: This is another way to describe the expected behavior of a LEFT JOIN, where unmatched rows from the orders table will have NULL values for columns from the customers table.
E. Incorrect.
Incorrect: Rows from the customers table without matching rows in the orders table will not appear in the result of a LEFT JOIN. This describes the behavior of a FULL OUTER JOIN.

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Databricks Data Engineer Associate Question 184

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