API with NestJS #16. Using the array data type with PostgreSQL and TypeORM

API with NestJS #16. Using the array data type with PostgreSQL and TypeORM

This article explores how the array data type works in PostgreSQL both through SQL queries and through TypeORM

  • 1.  API with NestJS #1. Controllers, routing and the module structure
  • 2.  API with NestJS #2. Setting up a PostgreSQL database with TypeORM
  • 3.  API with NestJS #3. Authenticating users with bcrypt, Passport, JWT, and cookies
  • 4.  API with NestJS #4. Error handling and data validation
  • 5.  API with NestJS #5. Serializing the response with interceptors
  • 6.  API with NestJS #6. Looking into dependency injection and modules
  • 7.  API with NestJS #7. Creating relationships with Postgres and TypeORM
  • 8.  API with NestJS #8. Writing unit tests
  • 9.  API with NestJS #9. Testing services and controllers with integration tests
  • 10.  API with NestJS #10. Uploading public files to Amazon S3
  • 11.  API with NestJS #11. Managing private files with Amazon S3
  • 12.  API with NestJS #12. Introduction to Elasticsearch
  • 13.  API with NestJS #13. Implementing refresh tokens using JWT
  • 14.  API with NestJS #14. Improving performance of our Postgres database with indexes
  • 15.  API with NestJS #15. Defining transactions with PostgreSQL and TypeORM
  • 16. API with NestJS #16. Using the array data type with PostgreSQL and TypeORM
  • 17.  API with NestJS #17. Offset and keyset pagination with PostgreSQL and TypeORM
  • 18.  API with NestJS #18. Exploring the idea of microservices
  • 19.  API with NestJS #19. Using RabbitMQ to communicate with microservices
  • 20.  API with NestJS #20. Communicating with microservices using the gRPC framework
  • 21.  API with NestJS #21. An introduction to CQRS
  • 22.  API with NestJS #22. Storing JSON with PostgreSQL and TypeORM
  • 23.  API with NestJS #23. Implementing in-memory cache to increase the performance
  • 24.  API with NestJS #24. Cache with Redis. Running the app in a Node.js cluster
  • 25.  API with NestJS #25. Sending scheduled emails with cron and Nodemailer
  • 26.  API with NestJS #26. Real-time chat with WebSockets
  • 27.  API with NestJS #27. Introduction to GraphQL. Queries, mutations, and authentication
  • 28.  API with NestJS #28. Dealing in the N + 1 problem in GraphQL
  • 29.  API with NestJS #29. Real-time updates with GraphQL subscriptions
  • 30.  API with NestJS #30. Scalar types in GraphQL

Storing arrays is not an obvious thing in the world of SQL databases. Solutions such as MySQL, MariaDB, or Microsoft SQL Server don’t have a straightforward column type for arrays.

This article explores how the array data type works in PostgreSQL both through SQL queries and through TypeORM. By learning how to operate on arrays through SQL, we can better understand what the Postgres database is capable of. This will helps us quite a bit in using arrays through TypeORM.

The capabilities of the array data type in Postgres

Because databases such as MySQL don’t have an array data type, we might have had to work around this issue. One solution would be to create additional tables to store data that we would conceptualize as an array. Another solution would be to utilize the JSON data type available in MySQL and PostgreSQL.

To define the array data type column, we can append the square brackets or use the ARRAY keyword. Let’s play with our  post table a bit and add the  paragraphs column instead of  content.

ALTER TABLE post

DROP COLUMN content,

ADD COLUMN paragraphs text[]

ALTER TABLE post

DROP COLUMN content ,

ADD COLUMN paragraphs text ARRAY

The text is a column data type that stores strings of any length

Although we could provide the array’s size, it does not affect the behavior of the database and might only serve as documentation.

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