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Node.js - PostgreSQL CASE statement

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evangeline
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In this article, we would like to show you how to use PostgresΒ CASE statementΒ inΒ Node.js.

Node.js - PostgreSQL CASE statement
Data used in the example - HeidiSQL

Note:Β 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 getSalaryOverview = async () => {
	const query = `
        SELECT "name", "salary",
        CASE 
            WHEN "salary" > 6000 THEN 'Salary greater than 6000$'
            WHEN "salary" > 4000 THEN 'Salary greater than 4000$'
            WHEN "salary" >= 2000 THEN 'Salary greater than 2000$'
            ELSE 'Salary less than 2000$'
        END AS "Salary information"
        FROM "users";`;
    try {
        await client.connect();    // gets connection
        const { rows } = await client.query(query); // sends query
        console.table(rows);
    } catch (error) {
        console.error(error.stack);
    } finally {
        await client.end();        // closes connection
    }
};

getSalaryOverview();

Result:Β 

β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
β”‚ (index) β”‚    name     β”‚  salary   β”‚     Salary information      β”‚
β”œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”Όβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”Όβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”Όβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€
β”‚    0    β”‚   'John'    β”‚ '3512.00' β”‚ 'Salary greater than 2000$' β”‚
β”‚    1    β”‚   'Chris'   β”‚ '1344.00' β”‚  'Salary less than 2000$'   β”‚
β”‚    2    β”‚   'Kate'    β”‚ '6574.00' β”‚ 'Salary greater than 6000$' β”‚
β”‚    3    β”‚  'Ailisa'   β”‚ '6500.00' β”‚ 'Salary greater than 6000$' β”‚
β”‚    4    β”‚ 'Gwendolyn' β”‚ '4200.00' β”‚ 'Salary greater than 4000$' β”‚
β”‚    5    β”‚   'Simon'   β”‚ '3320.00' β”‚ 'Salary greater than 2000$' β”‚
β”‚    6    β”‚  'Taylor'   β”‚ '1500.00' β”‚  'Salary less than 2000$'   β”‚
β”‚    7    β”‚  'Andrew'   β”‚ '2100.00' β”‚ 'Salary greater than 2000$' β”‚
β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

Database preparation

create_tables.sqlΒ 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.sqlΒ 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 `name`, `salary`,
CASE 
	WHEN `salary` > 6000 THEN 'Salary greater than 6000$'
	WHEN `salary` > 4000 THEN 'Salary greater than 4000$'
	WHEN `salary` >= 2000 THEN 'Salary greater than 2000$'
	ELSE 'Salary less than 2000$'
END AS 'Salary information'
FROM `users`;

Node.js - PostgreSQL

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