Question

A data engineer is building a Gold-layer table that reports the number of unique customers who placed at least one order on each calendar day. The Silver table `orders` has columns `order_date`, `customer_id`, and `order_amount`. Which Spark SQL query correctly produces one row per day with the count of distinct customers?

Accepted Answer

SELECT order_date, COUNT(DISTINCT customer_id) AS unique_customers FROM orders GROUP BY order_date

Answer

SELECT order_date, COUNT(customer_id) AS unique_customers FROM orders GROUP BY order_date

Answer

SELECT DISTINCT order_date, COUNT(customer_id) AS unique_customers FROM orders

Answer

SELECT order_date, COUNT(DISTINCT customer_id) AS unique_customers FROM orders