Sequelize Basics.ts

//Firstly, we create a Sequelize instance with an options object
export const databaseProviders = [
  {
    provide: 'SEQUELIZE',
    useFactory: async () => {
      const sequelize = new Sequelize({
        dialect: 'postgres',
        host: 'localhost',
        port: 5432,
        username: 'postgres',
        password: 'postgres',
        database: 'postgres',
      });
      sequelize.addModels([Cat]); // Add all models
      await sequelize.sync(); //  Sync database tables
      return sequelize;
    },
  },
];

// Then, export the provider to make it accessible
@Module({
  providers: [...databaseProviders],
  exports: [...databaseProviders],
})
export class DatabaseModule {}

// Define model entity, each represent a table in the database
@Table
export class Cat extends Model {
  @Column
  name: string;

  @Column
  age: number;

  @Column
  breed: string;
}
// Create a repository provider
export const catsProviders = [
  {
    provide: 'CATS_REPOSITORY',
    useValue: Cat,
  },
];
// In service, we inject the repository
export const catsProviders = [
  {
    provide: 'CATS_REPOSITORY',
    useValue: Cat,
  },
];
// Then, we can perform database operations
this.catsRepository.findAll<Cat>();