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A retail company stores customer purchase history in a relational database. The database contains a table 'transactions' with columns: transaction_id, customer_id, product_id, quantity, price, and transaction_date. A data analyst needs to create a report that shows total revenue per customer for the last quarter. Which data concept describes the relationship between customer_id and total revenue?
Total revenue is calculated by summing (quantity * price) for each customer, making it a derived attribute because it is computed from existing stored data (quantity and price) rather than stored directly. In the context of the 'transactions' table, customer_id is a stored key, b…Read full explanation
A healthcare database stores patient records. Each patient has a unique patient_id, and the database includes a table 'visits' with visit_id, patient_id, visit_date, and diagnosis_code. To ensure data integrity, which constraint should be applied to the patient_id column in the 'visits' table?
Option B is correct because a foreign key constraint ensures that patient_id in visits references a valid patient_id in the patient table. Option A is wrong because primary key ensures uniqueness in its own table. Option C is wrong because unique constraint prevents duplicates. O…Read full explanation
A data engineer is designing a data warehouse for a multinational corporation. The company has sales data from different regions with varying currencies and date formats. To ensure consistency, which data concept should be applied to standardize the data before loading into the warehouse?
Data transformation is the correct concept because it involves converting data from source formats (e.g., different currencies and date formats) into a consistent, standardized format before loading into the data warehouse. This process includes applying conversion rules, such as…Read full explanation
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