SUM, AVG, MIN, and MAX

SUM and AVG work with numeric values

SUM adds values together, while AVG calculates their average.

SELECT
    SUM(amount) AS total_amount,
    AVG(amount) AS average_amount
FROM orders
WHERE status = 'PAID';

Both functions work only with rows that passed WHERE. NULL values in the aggregated expression are normally ignored.

MIN and MAX find the boundaries of a set

SELECT
    MIN(price) AS cheapest,
    MAX(price) AS most_expensive
FROM products;

MIN returns the smallest value, while MAX returns the largest. These functions are not limited to numbers: database systems can also compare dates and other ordered types.