How can window functions like lag() in PostgreSQL be used to efficiently compare rows in a database?

Window functions like lag() in PostgreSQL can be used to efficiently compare rows in a database by allowing you to access data from previous rows without the need for self-joins or subqueries. This can be useful for calculating the difference between consecutive rows, identifying trends, or finding patterns in the data.

SELECT
    id,
    value,
    lag(value) OVER (ORDER BY id) AS previous_value,
    value - lag(value) OVER (ORDER BY id) AS value_difference
FROM
    your_table;