- 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
- 31. API with NestJS #31. Two-factor authentication
- 32. API with NestJS #32. Introduction to Prisma with PostgreSQL
- 33. API with NestJS #33. Managing PostgreSQL relationships with Prisma
- 34. API with NestJS #34. Handling CPU-intensive tasks with queues
- 35. API with NestJS #35. Using server-side sessions instead of JSON Web Tokens
- 36. API with NestJS #36. Introduction to Stripe with React
- 37. API with NestJS #37. Using Stripe to save credit cards for future use
- 38. API with NestJS #38. Setting up recurring payments via subscriptions with Stripe
- 39. API with NestJS #39. Reacting to Stripe events with webhooks
- 40. API with NestJS #40. Confirming the email address
- 41. API with NestJS #41. Verifying phone numbers and sending SMS messages with Twilio
- 42. API with NestJS #42. Authenticating users with Google
- 43. API with NestJS #43. Introduction to MongoDB
- 44. API with NestJS #44. Implementing relationships with MongoDB
- 45. API with NestJS #45. Virtual properties with MongoDB and Mongoose
- 46. API with NestJS #46. Managing transactions with MongoDB and Mongoose
- 47. API with NestJS #47. Implementing pagination with MongoDB and Mongoose
- 48. API with NestJS #48. Definining indexes with MongoDB and Mongoose
- 49. API with NestJS #49. Updating with PUT and PATCH with MongoDB and Mongoose
- 50. API with NestJS #50. Introduction to logging with the built-in logger and TypeORM
- 51. API with NestJS #51. Health checks with Terminus and Datadog
- 52. API with NestJS #52. Generating documentation with Compodoc and JSDoc
- 53. API with NestJS #53. Implementing soft deletes with PostgreSQL and TypeORM
- 54. API with NestJS #54. Storing files inside a PostgreSQL database
- 55. API with NestJS #55. Uploading files to the server
- 56. API with NestJS #56. Authorization with roles and claims
- 57. API with NestJS #57. Composing classes with the mixin pattern
- 58. API with NestJS #58. Using ETag to implement cache and save bandwidth
- 59. API with NestJS #59. Introduction to a monorepo with Lerna and Yarn workspaces
- 60. API with NestJS #60. The OpenAPI specification and Swagger
- 61. API with NestJS #61. Dealing with circular dependencies
- 62. API with NestJS #62. Introduction to MikroORM with PostgreSQL
- 63. API with NestJS #63. Relationships with PostgreSQL and MikroORM
- 64. API with NestJS #64. Transactions with PostgreSQL and MikroORM
- 65. API with NestJS #65. Implementing soft deletes using MikroORM and filters
- 66. API with NestJS #66. Improving PostgreSQL performance with indexes using MikroORM
- 67. API with NestJS #67. Migrating to TypeORM 0.3
- 68. API with NestJS #68. Interacting with the application through REPL
- 69. API with NestJS #69. Database migrations with TypeORM
- 70. API with NestJS #70. Defining dynamic modules
- 71. API with NestJS #71. Introduction to feature flags
- 72. API with NestJS #72. Working with PostgreSQL using raw SQL queries
- 73. API with NestJS #73. One-to-one relationships with raw SQL queries
- 74. API with NestJS #74. Designing many-to-one relationships using raw SQL queries
- 75. API with NestJS #75. Many-to-many relationships using raw SQL queries
- 76. API with NestJS #76. Working with transactions using raw SQL queries
- 77. API with NestJS #77. Offset and keyset pagination with raw SQL queries
- 78. API with NestJS #78. Generating statistics using aggregate functions in raw SQL
- 79. API with NestJS #79. Implementing searching with pattern matching and raw SQL
- 80. API with NestJS #80. Updating entities with PUT and PATCH using raw SQL queries
- 81. API with NestJS #81. Soft deletes with raw SQL queries
- 82. API with NestJS #82. Introduction to indexes with raw SQL queries
- 83. API with NestJS #83. Text search with tsvector and raw SQL
- 84. API with NestJS #84. Implementing filtering using subqueries with raw SQL
- 85. API with NestJS #85. Defining constraints with raw SQL
- 86. API with NestJS #86. Logging with the built-in logger when using raw SQL
- 87. API with NestJS #87. Writing unit tests in a project with raw SQL
- 88. API with NestJS #88. Testing a project with raw SQL using integration tests
- 89. API with NestJS #89. Replacing Express with Fastify
- 90. API with NestJS #90. Using various types of SQL joins
- 91. API with NestJS #91. Dockerizing a NestJS API with Docker Compose
- 92. API with NestJS #92. Increasing the developer experience with Docker Compose
- 93. API with NestJS #93. Deploying a NestJS app with Amazon ECS and RDS
- 94. API with NestJS #94. Deploying multiple instances on AWS with a load balancer
- 95. API with NestJS #95. CI/CD with Amazon ECS and GitHub Actions
- 96. API with NestJS #96. Running unit tests with CI/CD and GitHub Actions
- 97. API with NestJS #97. Introduction to managing logs with Amazon CloudWatch
- 98. API with NestJS #98. Health checks with Terminus and Amazon ECS
- 99. API with NestJS #99. Scaling the number of application instances with Amazon ECS
- 100. API with NestJS #100. The HTTPS protocol with Route 53 and AWS Certificate Manager
- 101. API with NestJS #101. Managing sensitive data using the AWS Secrets Manager
- 102. API with NestJS #102. Writing unit tests with Prisma
- 103. API with NestJS #103. Integration tests with Prisma
- 104. API with NestJS #104. Writing transactions with Prisma
- 105. API with NestJS #105. Implementing soft deletes with Prisma and middleware
- 106. API with NestJS #106. Improving performance through indexes with Prisma
- 107. API with NestJS #107. Offset and keyset pagination with Prisma
- 108. API with NestJS #108. Date and time with Prisma and PostgreSQL
- 109. API with NestJS #109. Arrays with PostgreSQL and Prisma
- 110. API with NestJS #110. Managing JSON data with PostgreSQL and Prisma
- 111. API with NestJS #111. Constraints with PostgreSQL and Prisma
- 112. API with NestJS #112. Serializing the response with Prisma
- 113. API with NestJS #113. Logging with Prisma
- 114. API with NestJS #114. Modifying data using PUT and PATCH methods with Prisma
- 115. API with NestJS #115. Database migrations with Prisma
- 116. API with NestJS #116. REST API versioning
- 117. API with NestJS #117. CORS – Cross-Origin Resource Sharing
- 118. API with NestJS #118. Uploading and streaming videos
- 119. API with NestJS #119. Type-safe SQL queries with Kysely and PostgreSQL
- 120. API with NestJS #120. One-to-one relationships with the Kysely query builder
- 121. API with NestJS #121. Many-to-one relationships with PostgreSQL and Kysely
- 122. API with NestJS #122. Many-to-many relationships with Kysely and PostgreSQL
- 123. API with NestJS #123. SQL transactions with Kysely
- 124. API with NestJS #124. Handling SQL constraints with Kysely
- 125. API with NestJS #125. Offset and keyset pagination with Kysely
- 126. API with NestJS #126. Improving the database performance with indexes and Kysely
- 127. API with NestJS #127. Arrays with PostgreSQL and Kysely
- 128. API with NestJS #128. Managing JSON data with PostgreSQL and Kysely
- 129. API with NestJS #129. Implementing soft deletes with SQL and Kysely
- 130. API with NestJS #130. Avoiding storing sensitive information in API logs
- 131. API with NestJS #131. Unit tests with PostgreSQL and Kysely
- 132. API with NestJS #132. Handling date and time in PostgreSQL with Kysely
- 133. API with NestJS #133. Introducing database normalization with PostgreSQL and Prisma
- 134. API with NestJS #134. Aggregating statistics with PostgreSQL and Prisma
- 135. API with NestJS #135. Referential actions and foreign keys in PostgreSQL with Prisma
- 136. API with NestJS #136. Raw SQL queries with Prisma and PostgreSQL range types
- 137. API with NestJS #137. Recursive relationships with Prisma and PostgreSQL
- 138. API with NestJS #138. Filtering records with Prisma
- 139. API with NestJS #139. Using UUID as primary keys with Prisma and PostgreSQL
- 140. API with NestJS #140. Using multiple PostgreSQL schemas with Prisma
- 141. API with NestJS #141. Getting distinct records with Prisma and PostgreSQL
- 142. API with NestJS #142. A video chat with WebRTC and React
- 143. API with NestJS #143. Optimizing queries with views using PostgreSQL and Kysely
- 144. API with NestJS #144. Creating CLI applications with the Nest Commander
- 145. API with NestJS #145. Securing applications with Helmet
- 146. API with NestJS #146. Polymorphic associations with PostgreSQL and Prisma
- 147. API with NestJS #147. The data types to store money with PostgreSQL and Prisma
- 148. API with NestJS #148. Understanding the injection scopes
- 149. API with NestJS #149. Introduction to the Drizzle ORM with PostgreSQL
- 150. API with NestJS #150. One-to-one relationships with the Drizzle ORM
- 151. API with NestJS #151. Implementing many-to-one relationships with Drizzle ORM
- 152. API with NestJS #152. SQL constraints with the Drizzle ORM
- 153. API with NestJS #153. SQL transactions with the Drizzle ORM
- 154. API with NestJS #154. Many-to-many relationships with Drizzle ORM and PostgreSQL
- 155. API with NestJS #155. Offset and keyset pagination with the Drizzle ORM
- 156. API with NestJS #156. Arrays with PostgreSQL and the Drizzle ORM
- 157. API with NestJS #157. Handling JSON data with PostgreSQL and the Drizzle ORM
- 158. API with NestJS #158. Soft deletes with the Drizzle ORM
- 159. API with NestJS #159. Date and time with PostgreSQL and the Drizzle ORM
- 160. API with NestJS #160. Using views with the Drizzle ORM and PostgreSQL
- 161. API with NestJS #161. Generated columns with the Drizzle ORM and PostgreSQL
- 162. API with NestJS #162. Identity columns with the Drizzle ORM and PostgreSQL
- 163. API with NestJS #163. Full-text search with the Drizzle ORM and PostgreSQL
- 164. API with NestJS #164. Improving the performance with indexes using Drizzle ORM
- 165. API with NestJS #165. Time intervals with the Drizzle ORM and PostgreSQL
- 166. API with NestJS #166. Logging with the Drizzle ORM
- 167. API with NestJS #167. Unit tests with the Drizzle ORM
- 168. API with NestJS #168. Integration tests with the Drizzle ORM
- 169. API with NestJS #169. Unique IDs with UUIDs using Drizzle ORM and PostgreSQL
- 170. API with NestJS #170. Polymorphic associations with PostgreSQL and Drizzle ORM
- 171. API with NestJS #171. Recursive relationships with Drizzle ORM and PostgreSQL
- 172. API with NestJS #172. Database normalization with Drizzle ORM and PostgreSQL
- 173. API with NestJS #173. Storing money with Drizzle ORM and PostgreSQL
- 174. API with NestJS #174. Multiple PostgreSQL schemas with Drizzle ORM
- 175. API with NestJS #175. PUT and PATCH requests with PostgreSQL and Drizzle ORM
- 176. API with NestJS #176. Database migrations with the Drizzle ORM
- 177. API with NestJS #177. Response serialization with the Drizzle ORM
When we design the architecture of our database, we usually end up with tables that relate to each other in some way. Managing such relationships is one of the crucial aspects of working with SQL databases. In this article, we explain the one-to-one relationship and handle it using Kysely with PostgreSQL and NestJS.
You can see the full code from this article in this repository.
Introducing the one-to-one relationship
When storing the information about addresses, we could add the address_street, address_city, and address_country to our users table. However, it might make sense to split it into a separate table called addresses and implement a one-to-one relationship. When we implement the one-to-one relationship, a particular row from the first table has one matching row from the second table and the other way around.
In the above situation, the addess is optional. The case of a one-to-one relationship that is optional can also be referred to as one-to-zero-or-one relationship.
While one-to-one might not be the most common type of relationship, there is a chance we might encounter it when working with various databases. When deciding on whether or not to create a one-to-one relationship, there are quite a few factors to take into consideration. I suggest reading this question on StackOverflow if you want to encounter various opinions to help you make your own choice.
Managing one-to-one relationships with Kysely
In the previous part of this series, we learned how to use Kysely to manage migrations. Let’s start by creating a new migration to add the addresses table and develop a relationship with the users.
20230813192709_add_addresses_table.ts
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import { Kysely } from 'kysely'; export async function up(database: Kysely<unknown>): Promise<void> { await database.schema .createTable('addresses') .addColumn('id', 'serial', (column) => { return column.primaryKey(); }) .addColumn('street', 'text') .addColumn('city', 'text') .addColumn('country', 'text') .execute(); await database.schema .alterTable('users') .addColumn('address_id', 'integer', (column) => { return column.unique().references('addresses.id'); }) .execute(); } export async function down(database: Kysely<unknown>): Promise<void> { await database.schema.dropTable('country').execute(); await database.schema.alterTable('users').dropColumn('address_id'); } |
In the above code, we create the addresses table. We also add the address_id column to the existing users table as a foreign key that refers to the primary key of the addresses table. Thanks to that, PostgreSQL recognizes there is a connection between our tables.
Also, in our application, only one user can refer to a particular address. Because of that, we add the unique constraint to the address_id column. Thanks to that, trying to connect more than one user to the same row in the addresses table would throw an error.
We can now add the address Table to the TypeScript definition of our database.
addressesTable.ts
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import { Generated } from 'kysely'; export interface AddressesTable { id: Generated<number>; street: string | null; city: string | null; country: string | null; } |
Let’s also add the address_id to the definition of our users table.
usersTable.ts
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import { Generated } from 'kysely'; export interface UsersTable { id: Generated<number>; email: string; name: string; password: string; address_id: number | null; } |
The last step is to ensure that both tables are added to our Tables interface.
database.ts
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import { ArticlesTable } from '../articles/articlesTable'; import { Kysely } from 'kysely'; import { UsersTable } from '../users/usersTable'; import { AddressesTable } from '../users/addressesTable'; interface Tables { articles: ArticlesTable; users: UsersTable; addresses: AddressesTable; } export class Database extends Kysely<Tables> {} |
Inserting rows into two tables in a single query
We want to insert the user and the address into the database simultaneously. One way of doing that is to create a Common Table Expression Query using the WITH statement. With this approach, we can create both the address and the user in a single, atomic SQL query and either succeeds completely or fails as a whole. The address won’t be stored in the database if something goes wrong when inserting the user.
users.repository.ts
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import { Injectable } from '@nestjs/common'; import { User } from './user.model'; import { CreateUserDto } from './dto/createUser.dto'; import { Database } from '../database/database'; @Injectable() export class UsersRepository { constructor(private readonly database: Database) {} // ... async createWithAddress(userData: CreateUserDto) { const databaseResponse = await this.database .with('created_address', (database) => { return database .insertInto('addresses') .values({ street: userData.address?.street, city: userData.address?.city, country: userData.address?.country, }) .returningAll(); }) .insertInto('users') .values((expressionBuilder) => { return { password: userData.password, email: userData.email, name: userData.name, address_id: expressionBuilder .selectFrom('created_address') .select('id'), }; }) .returning((expressionBuilder) => { return [ 'id', 'email', 'name', 'password', 'address_id', expressionBuilder .selectFrom('created_address') .select('street') .as('address_street'), expressionBuilder .selectFrom('created_address') .select('city') .as('address_city'), expressionBuilder .selectFrom('created_address') .select('country') .as('address_country'), ]; }) .executeTakeFirstOrThrow(); return new User(databaseResponse); } } |
Thanks to using the with function from Kysely instead of writing the SQL query manually, our code is type-safe. For example, TypeScript would complain if we would make a typo in the following section of the code:
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address_id: expressionBuilder .selectFrom('created_address') .select('wrong_column_name') |
Let’s use the new createWithAddress method whenever the user’s signing-up data contains the address.
users.service.ts
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import { Injectable } from '@nestjs/common'; import { CreateUserDto } from './dto/createUser.dto'; import { UsersRepository } from './users.repository'; import { isRecord } from '../utils/isRecord'; import { PostgresErrorCode } from '../database/postgresErrorCode.enum'; import { UserAlreadyExistsException } from './exceptions/userAlreadyExists.exception'; @Injectable() export class UsersService { constructor(private readonly usersRepository: UsersRepository) {} // ... async create(user: CreateUserDto) { try { if (user.address) { return await this.usersRepository.createWithAddress(user); } return await this.usersRepository.create(user); } catch (error) { if (isRecord(error) && error.code === PostgresErrorCode.UniqueViolation) { throw new UserAlreadyExistsException(user.email); } throw error; } } } |
Above, we’re also checking if there was an error when creating a user because the provided email is occupied already. To do that, we created the PostgresErrorCode enum that contains various codes that PostgreSQL can emit when an error happens.
postgresErrorCode.enum.ts
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export enum PostgresErrorCode { UniqueViolation = '23505', } |
Error handling with PostgreSQL and Kysely is a topic that deserves a separate article.
Creating the models
Since our query now includes the address, we need to adjust our models.
adress.model.ts
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interface AddressModelData { id: number; street?: string | null; city?: string | null; country?: string | null; } export class Address { id: number; street: string | null; city: string | null; country: string | null; constructor({ id, street = null, city = null, country = null, }: AddressModelData) { this.id = id; this.street = street; this.city = city; this.country = country; } } |
We also need to use the above model in the User class.
user.model.ts
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import { Exclude } from 'class-transformer'; import { Address } from './address.model'; interface UserModelData { id: number; email: string; name: string; password: string; address_id?: number | null; address_street?: string | null; address_city?: string | null; address_country?: string | null; } export class User { id: number; email: string; name: string; @Exclude({ toPlainOnly: true }) password: string; address?: Address; constructor({ id, email, name, password, address_id = null, address_street = null, address_country = null, address_city = null, }: UserModelData) { this.id = id; this.email = email; this.name = name; this.password = password; if (address_id) { this.address = new Address({ id: address_id, street: address_street, city: address_city, country: address_country, }); } } } |
Thanks to all of the above, we can now sign up while providing the details of our address.
Joining the data from two tables
Our SQL queries can retrieve rows from multiple tables simultaneously and match them based on ids. To do that, we need to perform a join. The default type of join in SQL is the inner join.
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SELECT users.*, addresses.street as address_street, addresses.city as address_city, addresses.country as address_country FROM users JOIN addresses ON users.address_id = addresses.id WHERE email=$1 |
The crucial thing about the inner join is that it returns records that have matching values in both tables. In our database structure, the address is optional. Because of that, our query would not return a user that does not have an address, even if the user with the particular email is in our database.
To fix the above issue, we need to perform an outer join. Outer joins preserve the rows that don’t have matching values. In our case, we need to do the left join that returns all records from the left table and the matched records from the right table. The left table is the users, and the right table is the addresses.
users.repository.ts
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import { Injectable } from '@nestjs/common'; import { User } from './user.model'; import { Database } from '../database/database'; @Injectable() export class UsersRepository { constructor(private readonly database: Database) {} async getByEmail(email: string) { const databaseResponse = await this.database .selectFrom('users') .where('email', '=', email) .leftJoin('addresses', 'addresses.id', 'users.address_id') .select([ 'users.id as id', 'users.email as email', 'users.name as name', 'users.password as password', 'addresses.id as address_id', 'addresses.city as address_city', 'addresses.street as address_street', 'addresses.country as address_country', ]) .executeTakeFirst(); if (databaseResponse) { return new User(databaseResponse); } } // ... } |
Thanks to using Kysely, the above code is type-safe. TypeScript would prevent us from making a typo in 'addresses.country as address_country', for example.
By using the left join, we ensure that our query works as expected for users that don’t have addresses.
Summary
In this article, we explained the one-to-one relationships using the example of users and addresses. We’ve also learned how to implement them when working with PostgreSQL and Kysely to generate SQL queries in a type-safe manner. While doing that, we used common table expressions to ensure we created both the user and the address in a single SQL query. We also had the chance to understand the difference between inner and outer joins. There is still much to learn when implementing relationships with Kysely and PostgreSQL, so stay tuned!
Great series of tutos! Would be cool to create a blog post using DrizzleORM! 🙂