PostgreSQL - Subqueries in PostgreSQL
You want to find customers who have placed orders but exclude those who only ordered products priced below 50. Which query correctly uses
EXISTS to achieve this?You want to find customers who have placed orders but exclude those who only ordered products priced below 50. Which query correctly uses EXISTS to achieve this?
hard📝 Application Q8 of 15
Step-by-Step Solution
Solution:
Step 1: Understand the requirement
We want customers with orders for products priced 50 or more, excluding those with only cheaper products.Step 2: Analyze each option
SELECT * FROM customers WHERE EXISTS (SELECT 1 FROM orders JOIN products ON orders.product_id = products.id WHERE orders.customer_id = customers.id AND products.price >= 50); correctly joins orders and products, filters by price >= 50, and checks existence per customer.Final Answer:
SELECT * FROM customers WHERE EXISTS (SELECT 1 FROM orders JOIN products ON orders.product_id = products.id WHERE orders.customer_id = customers.id AND products.price >= 50); -> Option DQuick Check:
EXISTS with join and price filter = B [OK]
Quick Trick: Use EXISTS with JOIN and condition to filter related rows [OK]
Common Mistakes:
- Filtering on wrong table or column
- Using NOT EXISTS incorrectly
- Ignoring product price condition
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