❌ #SQLAntiPattern: Бесконечные вложенные подзапросы

Многие новички пишут код с множеством уровней вложенности:

-- Сложный для понимания запрос
SELECT *
FROM (
  SELECT * 
  FROM (
    SELECT * 
    FROM products 
    WHERE category_id IN (
      SELECT id 
      FROM categories 
      WHERE active = true
    )
  ) AS active_products
  WHERE price > 100
) AS expensive_products
WHERE stock_quantity > 0;

✅ Лучшее решение - использовать CTE (Common Table Expressions)

WITH active_categories AS (
  SELECT id 
  FROM categories 
  WHERE active = true
),
active_products AS (
  SELECT * 
  FROM products 
  WHERE category_id IN (SELECT id FROM active_categories)
),
expensive_products AS (
  SELECT * 
  FROM active_products 
  WHERE price > 100
)
SELECT * 
FROM expensive_products
WHERE stock_quantity > 0;

💡 CTE делают код намного читабельнее и легче для сопровождения!

#CleanCode #SQLRefactoring