PostgreSQL - average value for grouped rows

In this article, we would like to show you how to find avg value for grouped rows in PostgreSQL.

Quick solution:

SELECT "column1", AVG("column2")
FROM "table_name"
GROUP BY "column1";

Practical example

To show how to find avg value for grouped rows, we will use the following table:

Note:

At the end of this article you can find database preparation SQL queries.

Example

In this example, we will select the average salary value for each department.

Query:

SELECT department_id, AVG(salary) AS 'avg_salary'
FROM "users"
GROUP BY "department_id";

Result:

Database preparation

create_tables.sql file:

CREATE TABLE "users" (
	"id" SERIAL,
	"name" VARCHAR(50) NOT NULL,
	"surname" VARCHAR(50) NOT NULL,
	"email" VARCHAR(100),
	"department_id" INTEGER,
    "salary" DECIMAL(15,2) NOT NULL,
	PRIMARY KEY ("id")
);

insert_data.sql file:

INSERT INTO "users"
	( "name", "surname", "email", "department_id", "salary")
VALUES
	('John', 'Stewart', 'john@email.com', 1, '3512.00'),
	('Chris', 'Brown', 'chris@email.com', 2, '1344.00'),
	('Kate', 'Lewis', NULL, 3, '6574.00'),
	('Ailisa', 'Gomez', 'ailisa@email.com', 3, '6500.00'),
	('Gwendolyn', 'James', NULL, 2, '4200.00'),
	('Simon', 'Collins', NULL, 1, '3320.00'),
	('Taylor', 'Martin', NULL, 2, '1500.00'),
	('Andrew', 'Thompson', 'andrew@email.com', 1, '2100.00');