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Node.js - PostgreSQL ALTER TABLE - Drop column

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Created by:
Dirask Admin - MR
1340

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

MySQL - example data used with ALTER TABLE statement
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: 'postgres',
    database: 'database_name',
    password: 'password',
    port: 5432,
});

const DropColumn = async () => {
	const query = `ALTER TABLE "users"
                   DROP COLUMN IF EXISTS "department_id";`;
    try {
        await client.connect();    // gets connection
        await client.query(query); // sends query
    } catch (error) {
        console.error(error.stack);
    } finally {
        await client.end();        // closes connection
    }
};

DropColumn();

Result: 

Node.js - PostgreSQL ALTER TABLE - Drop column
Postgres - ALTER TABLE results in HeidiSQL

Note:

If we want to delete a column that does not exist, PostgreSQL will display an error. To be prepared for this and only remove the column if it exists, add IF EXISTS, then PostgreSQL will issue only a notice.

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"
DROP COLUMN IF EXISTS "department_id"

Node.js - PostgreSQL

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