𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝗲𝗿: 
You have 2 minutes to solve this SQL query.

Find the product(s) that have never been ordered.

Tables: 
products(product_id, product_name) 
order_details(order_id, product_id, quantity)

𝗠𝗲: Challenge accepted! 💪 
SELECT 
    p.product_id, 
    p.product_name 
FROM products p 
LEFT JOIN order_details od 
    ON p.product_id = od.product_id 
WHERE od.product_id IS NULL;

💡 Explanation: 
This query finds all products that do not have a matching record in the order_details table.

LEFT JOIN returns all products, regardless of whether they've been ordered. Products without matching orders will have NULL values for columns from order_details. WHERE od.product_id IS NULL filters only those products that have never been ordered.

This question tests your understanding of: LEFT JOIN, NULL handling, Finding unmatched records

🎯 Expected Output Example 
Product ID   Product Name 
104   Wireless Mouse 
118   USB Hub 
125   Laptop Stand 

🚀 Alternative Using NOT EXISTS 
SELECT 
    p.product_id, 
    p.product_name 
FROM products p 
WHERE NOT EXISTS ( 
    SELECT 1 
    FROM order_details od 
    WHERE od.product_id = p.product_id 
);

NOT EXISTS is often preferred because it handles NULL values correctly and can perform better than other approaches in many database systems.

🚀 Tip for SQL Job Seekers: 
Whenever you're asked to find records that don't exist in another table, consider these approaches: 

LEFT JOIN ... IS NULL, NOT EXISTS ✅ (often the best choice), NOT IN (be cautious with NULL values)

Knowing the pros and cons of each approach is a common interview discussion point.

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