Sequelize with typescript

Sequelize is a promise-based Node.js ORM for Postgres, MySQL, MariaDB, SQLite and Microsoft SQL Server. It features solid transaction support, relations, eager and lazy loading, read replication and more.

More info is available on https://sequelize.org/master/index.html

Steps to setup Sequelize with Typescript is as follows:

Lets Start,

1. Install sequelize npm module
   npm install --save sequelize
2. Install database driver which is required for connection
   One of the following as required:
   # npm install — save pg pg-hstore //Postgres
   # npm install — save mysql2
   # npm install — save mariadb
   # npm install — save sqlite3
   # npm install — save tedious // Microsoft SQL Server
3. Create folder structure as shown below,

Folder Structure

Sequelize connection details and database models will be under database folder. Sequelize will look for the database directory and its sub-directories. It’s sequelize default structure
database folder will have sub-directories,
- attributes: this folder carries all the required model interface
- migrations: this folder carries database migrations
- models: this folder carries database models
- seeders: this folder carries data to be initialized once database is synced
- SequelizeConnection.ts: this file will be used to setup database connection using sequelize

Sequelize connection setup:
Connection object needs to be passed to sequelize which consist of following details,

• host
• port
• database-name
• username
• password
• dialect (default mysql)
• schema

Putting this into SequelizeConnection.ts class,

For more options, you can visit https://sequelize.org/master/class/lib/sequelize.js~Sequelize.html#instance-constructor-constructor

Create a small connection method which can be called to establish the connection,

Now, lets call the connect method in our app.ts

Run the app.ts file and you can see the below logs executing on terminal,

Congrats! We have successfully connected to our database using sequelize.

We’ll design a simple database with few tables and it’s association.
Consider a Organization having employees and each employee has different departments

Organization database design

We’ll first create different model attributes,

Create Organization.ts, UserDetails.ts and Department.ts file in attributes directory

and add the code as shown below in each file,

UserDetails.ts

Department.ts

Organization.ts

index.ts

Lets have a look how to create model for these attributes,

Create similar files models directory

Start adding the code as shown below,

Department.ts

UserDetails.ts

Organization.ts

index.ts

It’s time to sync models in our database. Add the below piece of code to app.ts file,

app.ts

Now run the server again and you’ll find the below logs executing on terminal

You’ll be able to see the tables created in your database

You can find the whole code in below github repo,
https://github.com/rishabh31845/postgres-sequelize.git

Thanks!!!