Node.js - PostgreSQL Calculate average of column values and display the result with no decimals

In this article, we would like to show you how to calculate the average of column values and display the result with no decimals in the Postgres database from Node.js level.

Note: at the end of this article you can find database preparation SQL queries.

const { Client } = require('pg');

const client = new Client({
    host: '127.0.0.1',
    user: 'my_username',
    database: 'my_database',
    password: 'my_password',
    port: 5432,
});

const fetchRoundSalary = async (decimalPlaces) => {
	const query = `
            SELECT ROUND(AVG("salary"), $1)
            FROM "users";
    `;
    await client.connect();   // creates connection
    try {
        const { rows } =  await client.query(query, [decimalPlaces]);  // sends query
        return rows;
    } finally {
        await client.end();   // closes connection
    }
};

fetchRoundSalary(0)
    .then(result => console.log(result))
    .catch(error => console.error(error.stack));

Result: 

[ { round: '3631' } ]

Database preparation

create_tables.sql file:

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

insert_data.sql file:

INSERT INTO "users"
	( "name", "surname", "department_id", "salary")
VALUES
	('John', 'Stewart', 1, '3512.00'),
	('Chris', 'Brown', 2, '1344.00'),
	('Kate', 'Lewis', 3, '6574.00'),
	('Ailisa', 'Gomez', NULL, '6500.00'),
	('Gwendolyn', 'James', 2, '4200.00'),
	('Simon', 'Cousersllins', 4, '3320.00'),
	('Taylor', 'Martin', 2, '1500.00'),
	('Andrew', 'Thompson', NULL, '2100.00');

Native SQL query (used in the above example):

SELECT ROUND(AVG("salary"), 0)
FROM "users";