Node.js - PostgreSQL LOWER()

In this article, we would like to show you how to convert a string to lower case using LOWER() function 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 fetchLowerCaseNames = async () => {
	const query = `    
            SELECT LOWER("name") AS "Lowercase names" 
            FROM "users";
    `;
    await client.connect();  // creates connection
    try {
        const { rows } = await client.query(query);  // sends query
        return rows;
    } finally {
        await client.end();  // closes connection
    }
};

fetchLowerCaseNames()
    .then(result => console.table(result))
    .catch(error => console.error(error.stack));

Result: 

┌─────────┬─────────────────┐
│ (index) │ Lowercase names │
├─────────┼─────────────────┤
│    0    │     'john'      │
│    1    │     'chris'     │
│    2    │     'kate'      │
│    3    │    'ailisa'     │
│    4    │   'gwendolyn'   │
│    5    │     'simon'     │
│    6    │    'taylor'     │
│    7    │    'andrew'     │
└─────────┴─────────────────┘

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 LOWER("name") AS "Lowercase names" 
FROM "users";