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Node.js - PostgreSQL MAX()

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Created by:
Mahir-Bright
501

In this article, we would like to show you how to get the maximum value of a set in the Postgres database from Node.js level.

Node.js - PostgreSQL MAX()
Data used in the example - HeidiSQL

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 fetchMaximumSalary = async () => {
	const query = `
            SELECT MAX("salary") AS "maximum salary" 
            FROM "users";
    `;
    await client.connect();   // creates connection
    try {
        const { rows } =  await client.query(query);  // sends query
        return rows;
    } finally {
        await client.end();   // closes connection
    }
};

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

Result: 

[ { 'maximum salary': '6574.00' } ]

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 MAX("salary") AS "maximum salary" 
FROM "users";
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Node.js - PostgreSQL

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