Bits of .NET

📊 WHERE filters rows. HAVING filters groups.

Need customers with 5+ orders? Groups with average > 100? HAVING clause filters aggregated results.

📝 Basic HAVING

-- Customers with 5+ orders
SELECT 
    customer_id,
    COUNT(*) as order_count
FROM orders
GROUP BY customer_id
HAVING COUNT(*) >= 5;

-- Departments with average salary > 50000
SELECT 
    department,
    AVG(salary) as avg_salary
FROM employees
GROUP BY department
HAVING AVG(salary) > 50000;

🎯 WHERE vs HAVING

-- WHERE (before GROUP BY)
SELECT 
    category,
    COUNT(*) as product_count
FROM products
WHERE price > 100  -- Filter rows before grouping
GROUP BY category;

-- HAVING (after GROUP BY)
SELECT 
    category,
    COUNT(*) as product_count
FROM products
GROUP BY category
HAVING COUNT(*) > 10;  -- Filter groups after aggregation

💡 Use Cases

• Find customers with high order volume
• Identify top-selling products
• Filter categories with enough products
• Find departments with high average salary
• Detect outliers in grouped data