Databricks Certified Data Engineer - Associate
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A data engineer needs to join two tables, customers and orders, on the condition c.customer_id = o.order_customer_id. The goal is to retrieve details of all customers, including those who have not placed any orders, along with the details of orders they have placed. Given the schemas of both tables, which join operation should be used to achieve this?
Explanation:
The correct answer is to use either a LEFT OUTER JOIN or a RIGHT OUTER JOIN. This is because the requirement is to fetch all records from the customers table (including those without orders) and only matching records from the orders table. A LEFT OUTER JOIN with customers on the left and orders on the right, or a RIGHT OUTER JOIN with orders on the left and customers on the right, will both satisfy the requirement. This approach ensures that all customers are included in the results, regardless of whether they have placed any orders.