[Edit]

Node.js - PostgreSQL WHERE clause

1 contributors

2 contributions

0 discussions

0 points

Created by:

Bess

571

In this article, we would like to show you how to use SQL WHERE clause in Node.js.

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

xxxxxxxxxx
 
const { Client } = require('pg');
​
const client = new Client({
    host: '127.0.0.1',
    user: 'postgres',
    database: 'database_name',
    password: 'password',
    port: 5432,
});
​
const fetchUsers = async (userName) => {
    const query = `SELECT * 
                   FROM "users"
                   WHERE "name" = $1`;
    try {
        await client.connect();                                 // gets connection
        const { rows } = await client.query(query, [userName]); // sends queries
        console.log(rows);
    } catch (error) {
        console.error(error.stack);
    } finally {
        await client.end();                                     // closes connection
    }
};
​
fetchUsers('Chris'); // username 

Result:

xxxxxxxxxx
 
[{ id: 2, name: 'Chris', role: 'moderator' }]

Multiple conditions example:

Edit

xxxxxxxxxx
 
const { Client } = require('pg');
​
const client = new Client({
    host: '127.0.0.1',
    user: 'postgres',
    database: 'dirask',
    password: 'password',
    port: 5432,
});
​
const fetchUsers = async (userName, userRole) => {
    const query = `SELECT * 
                   FROM "users"
                   WHERE "name" = $1 OR "role" = $2`;
    try {
        await client.connect(); // gets connection
        const { rows } = await client.query(query, [userName, userRole]); // sends queries
        console.log(rows);
    } catch (error) {
        console.error(error.stack);
    } finally {
        await client.end(); // closes connection
    }
};
​
fetchUsers('Chris', 'admin');

Result:

xxxxxxxxxx
 
[
    { id: 1, name: 'John', role: 'admin' },
    { id: 2, name: 'Chris', role: 'moderator' }
]

Database preparation

Edit

create_tables.sql file:

xxxxxxxxxx
 
CREATE TABLE "users" (
    "id" SERIAL,
    "name" VARCHAR(100) NOT NULL,
    "role" VARCHAR(15) NOT NULL,
    PRIMARY KEY ("id")
);

insert_data.sql file:

xxxxxxxxxx
 
INSERT INTO "users"
    ("name", "role")
VALUES
    ('John', 'admin'),
    ('Chris', 'moderator'),
    ('Kate', 'user'),
    ('Denis', 'moderator');