Aggregate Functions

Aggregate functions are single values computed from several rows of data. These functions include MAX, MIN, AVG, ROUND and SUM.

Check out the PostgreSQL’s full list of aggregate functions.

Common aggregate functions

Function	Description
Max	Computes the max of non-null input values.
Min	Computes the min of non-null input values.
Avg	Computes the average (arithmetic mean) of all the non-null input values.
Round	Rounds of all the non-null input values. Round can also specify the amount of decimal places with a second argument.
Sum	Computes the sum of the non-null input values.

Syntax

SELECT <aggregate-function>(<column>) FROM <table>;

Example #1

SELECT MAX(founded) FROM Companies;

The max value in the `founded` column.
Max
1998

Note: In some cases, an aggregate function can be used within another.
For example: ROUND(AVG(price), 2), rounds the average value of price up to two decimal places.

Example #2

SELECT hq, MIN(founded) FROM Companies 
GROUP BY hq;

The `hq` and `min` of each hq group
HQ	Min
United States	1923
Canada	1984