Use NOT EXISTS with correlated subqueries to find missing relationships
Which products had zero sales in Q4 2025 (October through December)? I want to see the product name, category, and unit price for every product that did NOT appear in any Q4 2025 sale. We might need to discontinue some underperformers.
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Use NOT EXISTS with a correlated subquery: WHERE NOT EXISTS (SELECT 1 FROM fact_sales WHERE product_id = p.product_id AND ...date conditions...)
Q4 2025 = sale_date between '2025-10-01' and '2025-12-31'
Be careful with the trailing-space duplicate 'Wireless Mouse ' — both versions should appear if they had no Q4 sales