PostgreSQL 18 reference · Aggregate Functions

PostgreSQL SUM() Function

Add up the non-NULL values in a group. Returns NULL, not 0, when there are no rows; wrap it in coalesce() if needed.

PostgreSQL 18

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Syntax

sum(expression)

Parameter	Description
`expression`	A column or expression.

bigint for integers, numeric for numeric, or NULL for no rows.

Totals per order

SELECT order_id, sum(quantity * unit_price) AS total
FROM order_items
GROUP BY order_id
ORDER BY total DESC
LIMIT 3;

Output

 order_id | total
----------+--------
        9 | 658.00
        4 | 408.90
        7 | 114.99
(3 rows)

Run this on your computer — see “Get Started” for setup.

No rows gives NULL

SELECT sum(price) AS raw, coalesce(sum(price), 0) AS safe
FROM products
WHERE price > 1000;

Output

 raw  | safe
------+------
 NULL |    0
(1 row)

Run this on your computer — see “Get Started” for setup.

AVG() · Return the average of the non-NULL values in a group. Integer input gives a numeric result with full precision.
COUNT() · Count rows: count(*) counts every row, count(x) skips NULLs, and count(DISTINCT x) counts unique values. Returns bigint.
COALESCE() · Return the first argument that isn't NULL. The standard way to replace NULL with a default.
SQL Aggregate Functions · tutorial
SQL GROUP BY · tutorial