Connect Multiple Databases in NodeJS Guide

Why do we use multiple databases ?

Multiple databases are useful in various situation

1) Microservice architecture: when each service has its own database.

2) Data segregation: You may need separate databases for different modules (e.g., userProducts, users).

3) Different Database Types: Connecting to both SQL and NoSQL databases in the same project.

Prerequisites

NodeJS installed.
TypeORM and the required database drivers installed.
Basic knowledge of NodeJS and TypeORM.

connect multiple database in node with typeORM

Follow This Steps:

1) Step 1: Install Required Dependencies.

Note: Ensure you have TypeORM and the necessary database drivers for the databases you’re connecting. Example, PostgreSQL and MySQL. npm install typeorm @nestjs/typeorm pg mysql2

2) Step 2: Create the Project

/src /entities userCart.ts userProducts.ts /modules userCart.module.ts product.module.ts app.module.ts main.ts /ormconfig ormconfig.userCart.ts ormconfig.product.ts

            Package.json

3) Step 3: Create ORM Configuration Files

- ormconfig.userCart.ts for userCart database import { DataSource } from 'typeorm';

import { userCarts } from '../oc/src/shared/entity/userCarts'; export const userCartDataSource = new DataSource({ type: 'postgres', // database you want to use host: 'localhost', port: 5432, username: 'userCart_db_user', password: 'userCart_db_password', database: 'userCart_db', entities: [userCarts], synchronize: true,

});

- ormconfig.product.ts for product database


           import { DataSource } from 'typeorm';

import { userProducts } from '/oc/src/shared/entity/userProducts';export const ProductDataSource = new DataSource({ type: 'mysql', // database you want to use host: 'localhost', port: 3306, username: 'userProducts_db_user', password: 'userProducts_db_password', database: 'userProducts_db', entities: [userProducts], synchronize: true,});

Step 4: Create Entities for Each Database

- userCart.ts Entity for the userCart Database

import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';

@Entity() export class userCart { @PrimaryGeneratedColumn() id: number; @Column(type: 'decimal',{ precision: 7, scale: 3, nullable: true}) totalItem: number;}

Product.ts Entity for the Product Database import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';

@Entity()

export class userProducts {

@PrimaryGeneratedColumn()

id: number;

@Column()

name: string; }

Step 5: Initialize Data Sources in Your Application

- made configuration in your app.module.ts import { Module } from '@nestjs/common';

import { TypeOrmModule } from '@nestjs/typeorm';import { userCartModule } from 'oc/module/userCart.module';import { ProductModule } from 'oc/module/userProducts.module';import { UserDataSource } from 'oc/ormconfig/ormconfig.userCart';import { ProductDataSource } from 'oc/ormconfig/ormconfig.userProducts';@Module({ imports: [ // Import the userCart database connection TypeOrmModule.forRootAsync({ useFactory: () => userCartDataSource.options, }), // Import the product database connection TypeOrmModule.forRootAsync({ useFactory: () => ProductDataSource.options, }), userCartModule, ProductModule, ],

})
export class AppModule {}

Step 6: Implement Modules for userCart and Product

- user.module.ts import { Module } from '@nestjs/common';

import { TypeOrmModule } from '@nestjs/typeorm';import { userCart } from '../oc/src/shared/entity/userCarts';import { userCartService } from 'oc/user.service';@Module({ imports: [TypeOrmModule.forFeature([userCart])], providers: [userCartService],})

export class userCartModule {}

product.module.ts

import { Module } from '@nestjs/common';

import { TypeOrmModule } from '@nestjs/typeorm';import { userProducts } from '../oc/src/shared/entity/userProducts';import { userProductservice } from 'oc/product.service';@Module({ imports: [TypeOrmModule.forFeature([userProducts])], providers: [userProductservice],})export class ProductModule {}

Step 7: Implement Services for Handling CRUD Operations

user.service.ts


import { Injectable } from '@nestjs/common';

import { InjectRepository } from '@nestjs/typeorm';import { Repository } from 'typeorm';import { userCart } from '../oc/src/shared/entity/userCarts';@Injectable()export class userCartService { constructor( @InjectRepository(userCart) private userCartRepository: Repository<userCart>, ) {} finduserCartDetails(): Promise<userCart[]> { return this.userCartRepository.find(); }}

product.service.ts

import { Injectable } from '@nestjs/common';

import { InjectRepository } from '@nestjs/typeorm';import { Repository } from 'typeorm';import { userProducts } from '../oc/src/shared/entity/userProducts';@Injectable()export class userProductsService { constructor( @InjectRepository(userProducts) private userProductsRepository: Repository<userProducts>, ) {} findAll(): Promise<userProducts:[]> { return this.productRepository.find(); } create(product: userProducts): Promise<userProducts> { return this.productRepository.save(product); }

Step 8: Run Your Application

npm run start

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