LAG and LEAD

LAG and LEAD access values from other rows.

LAG(column) - previous row's value LEAD(column) - next row's value

Compare to previous:

SELECT first_name, salary,
       LAG(salary) OVER (ORDER BY salary DESC) as prev_salary
FROM employees;

Perfect for:

• Year-over-year comparisons
• Day-over-day changes
• Finding gaps in data