FIRST_VALUE

1
SELECT 
2
  date,
3
  stock_symbol,
4
  price,
5
  FIRST_VALUE(price) OVER (
6
    PARTITION BY stock_symbol 
7
    ORDER BY date
8
  ) AS opening_price
9
FROM stock_prices;

1
SELECT 
2
  date,
3
  revenue,
4
  FIRST_VALUE(revenue) OVER (ORDER BY date) AS first_revenue,
5
  revenue - FIRST_VALUE(revenue) OVER (ORDER BY date) AS diff_from_start
6
FROM monthly_sales;

1
SELECT 
2
  category,
3
  product_name,
4
  price,
5
  price / FIRST_VALUE(price) OVER (
6
    PARTITION BY category ORDER BY price
7
  ) AS price_ratio
8
FROM products;