Connecting to Multiple Databases in NestJS with MySQL Without Defining Entities

Question

Connecting to Multiple Databases in NestJS with MySQL Without Defining Entities

If you're interested in learning about connecting to MySQL using TypeORM and defining Entities, the NestJS documentation has all the information you need.

In a situation where you have to connect to a MySQL server with multiple databases and need to execute SQL queries directly (without relying on the Entity layer) to fetch results, it can be challenging. Particularly if you also require running cross-database queries.

So, how can this be achieved using NestJS? Let's find out!

mysql sql typescript nestjs cross-database

Answer 1

Answer №1

To incorporate multiple databases, assign different names to each connection. You can achieve this by passing the database configuration directly in separate TypeOrmModule.forRoot({...}) imports or by utilizing a ormconfig.json config file. (However, please note that the ormconfig.json file may not fully support multiple databases as discussed in this thread.)

TypeOrmModule.forRoot({
  ...defaultOptions,
  name: 'personsConnection',
  ^^^^^^^^^^^^^^^^^^^^^^^^^^
  host:  'person_db_host',
  entities: [Person],
}),
TypeOrmModule.forRoot({
  ...defaultOptions,
  name: 'albumsConnection',
  ^^^^^^^^^^^^^^^^^^^^^^^^^
  host:  'album_db_host',
  // You can also leave the entities empty
  entities: [],
})

According to Kamil's comment, you can inject the TypeORM connection object with

@InjectConnection('albumsConnection'): Connection

and then utilize the QueryBuilder or the method query to execute raw SQL queries.

const rawData = await connection.query(`SELECT * FROM USERS`);

Answer 2

To incorporate multiple databases, assign different names to each connection. You can achieve this by passing the database configuration directly in separate TypeOrmModule.forRoot({...}) imports or by utilizing a ormconfig.json config file. (However, please note that the ormconfig.json file may not fully support multiple databases as discussed in this thread.)

TypeOrmModule.forRoot({
  ...defaultOptions,
  name: 'personsConnection',
  ^^^^^^^^^^^^^^^^^^^^^^^^^^
  host:  'person_db_host',
  entities: [Person],
}),
TypeOrmModule.forRoot({
  ...defaultOptions,
  name: 'albumsConnection',
  ^^^^^^^^^^^^^^^^^^^^^^^^^
  host:  'album_db_host',
  // You can also leave the entities empty
  entities: [],
})

According to Kamil's comment, you can inject the TypeORM connection object with

@InjectConnection('albumsConnection'): Connection

and then utilize the QueryBuilder or the method query to execute raw SQL queries.

const rawData = await connection.query(`SELECT * FROM USERS`);

Connecting to Multiple Databases in NestJS with MySQL Without Defining Entities

Answer №1

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