You want to find all customers who have placed orders for products in the 'Electronics' category. Given tables:
hard📝 Application Q15 of 15
SQL - Subqueries
You want to find all customers who have placed orders for products in the 'Electronics' category. Given tables: Customers(customer_id, name) Orders(order_id, customer_id, product_id) Products(product_id, category) Which query correctly uses a subquery with IN to get these customers?
ASELECT name FROM Customers WHERE customer_id IN (SELECT customer_id FROM Orders WHERE product_id IN (SELECT product_id FROM Products WHERE category = 'Electronics'));
BSELECT name FROM Customers WHERE customer_id = (SELECT customer_id FROM Orders WHERE product_id IN (SELECT product_id FROM Products WHERE category = 'Electronics'));
CSELECT name FROM Customers WHERE customer_id IN (SELECT product_id FROM Products WHERE category = 'Electronics');
DSELECT name FROM Customers WHERE customer_id IN (SELECT order_id FROM Orders WHERE product_id IN (SELECT product_id FROM Products WHERE category = 'Electronics'));
Step-by-Step Solution
Solution:
Step 1: Understand the relationships
Customers link to Orders by customer_id; Orders link to Products by product_id.
Step 2: Analyze the nested subqueries
The innermost subquery selects product_ids in 'Electronics'. The middle subquery selects customer_ids from Orders with those product_ids. The outer query selects customer names with those customer_ids.
Final Answer:
SELECT name FROM Customers WHERE customer_id IN (SELECT customer_id FROM Orders WHERE product_id IN (SELECT product_id FROM Products WHERE category = 'Electronics')); -> Option A
Quick Check:
Nested IN filters customers by Electronics orders [OK]
Quick Trick:Use nested IN for multi-level filtering [OK]
Common Mistakes:
MISTAKES
Using = instead of IN for multiple customer_ids
Comparing customer_id with product_id or order_id
Missing nested subquery for product filtering
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