Node.js - PostgreSQL ALTER TABLE - ALTER COLUMN

In this article, we would like to show you how to change column type in the existing table by ALTER TABLE in the Postgres database using Node.js.

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: 'postgres',
    database: 'database_name',
    password: 'password',
    port: 5432,
});

const changeColumnType = async () => {
	const query = `ALTER TABLE "users"
                   ALTER COLUMN "salary" TYPE VARCHAR;`;
    try {
        await client.connect();    // gets connection
        await client.query(query); // sends query
    } catch (error) {
        console.error(error.stack);
    } finally {
        await client.end();        // closes connection
    }
};

changeColumnType(); 

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):

ALTER TABLE "users"
ALTER COLUMN "salary" TYPE VARCHAR