Relations - 🌲 Sonamu

Relations define associations between Entities to ensure database referential integrity and enable type-safe join queries.

Relation Types Overview

Sonamu supports 4 Relation types:

BelongsToOne

N:1 relationship - Many reference oneExample: Post → User (multiple posts belong to one user)

OneToOne

1:1 relationship - One references oneExample: User ↔ Employee (user and employee info are 1:1 matched)

HasMany

1:N relationship - One owns manyExample: User → Posts (one user owns multiple posts)

ManyToMany

N:M relationship - Many-to-manyExample: Post ↔ Tag (many-to-many between posts and tags)

BelongsToOne

N:1 relationship - The current Entity belongs to another Entity.

Basic Usage

post.entity.json

{
  "id": "Post",
  "props": [
    {
      "type": "relation",
      "name": "user",
      "with": "User",
      "relationType": "BelongsToOne",
      "desc": "Author"
    }
  ]
}

Generated column: user_id (integer, not null) Database structure:

Options

Option	Type	Description	Default
`nullable`	boolean	Allow NULL	`false`
`useConstraint`	boolean	Use Foreign Key constraint	`true`
`onUpdate`	RelationOn	Action on referenced record update	`RESTRICT`
`onDelete`	RelationOn	Action on referenced record delete	`RESTRICT`
`customJoinClause`	string	Custom JOIN condition	-

RelationOn Options

Value	Description	Use Case
`CASCADE`	Change/delete child when parent changes	Delete posts when user is deleted
`SET NULL`	Set child’s FK to NULL when parent deleted	Set employee’s department to NULL when department deleted
`RESTRICT`	Prevent parent change/delete if children exist	Cannot delete user if posts exist
`NO ACTION`	Similar to RESTRICT, different check timing	-
`SET DEFAULT`	Set to default value when parent deleted	-

Example: nullable and CASCADE

{
  "type": "relation",
  "name": "department",
  "with": "Department",
  "relationType": "BelongsToOne",
  "nullable": true,
  "onDelete": "SET NULL",
  "desc": "Department"
}

Behavior:

department_id allows NULL
When department is deleted, employee’s department_id is set to NULL

TypeScript Usage

// Include relation in Subset
const posts = await this.puri()
  .select<PostSubsetA>("A")
  .many();

// Can access posts[0].user.username

OneToOne

1:1 relationship - Two Entities reference each other exactly once.

Basic Usage

OneToOne can be defined in two ways:

hasJoinColumn: true
hasJoinColumn: false

FK column is created in the current Entity.

employee.entity.json

{
  "id": "Employee",
  "props": [
    {
      "type": "relation",
      "name": "user",
      "with": "User",
      "relationType": "OneToOne",
      "hasJoinColumn": true,
      "onDelete": "CASCADE",
      "desc": "User account"
    }
  ]
}

Generated column: user_id (integer, unique, not null)Database structure:

users: id, username
employees: id, user_id (FK, UNIQUE), employee_number

The FK column must exist in the other Entity.

user.entity.json

{
  "id": "User",
  "props": [
    {
      "type": "relation",
      "name": "employee",
      "with": "Employee",
      "relationType": "OneToOne",
      "hasJoinColumn": false,
      "nullable": true,
      "desc": "Employee info"
    }
  ]
}

No column created - Uses user_id from Employee table

Options

Option	Type	Description	Default
`hasJoinColumn`	boolean	Whether to create FK column	required
`nullable`	boolean	Allow NULL (when hasJoinColumn: true)	`false`
`useConstraint`	boolean	FK constraint (when hasJoinColumn: true)	`true`
`onUpdate`	RelationOn	Action on update (when hasJoinColumn: true)	`RESTRICT`
`onDelete`	RelationOn	Action on delete (when hasJoinColumn: true)	`RESTRICT`
`customJoinClause`	string	Custom JOIN condition	-

Example: Bidirectional OneToOne

{
  "type": "relation",
  "name": "employee",
  "with": "Employee",
  "relationType": "OneToOne",
  "hasJoinColumn": false,
  "nullable": true
}

Relationship explained:

User can optionally have an Employee (nullable)
Employee must have a User (not null)
When User is deleted, Employee is also deleted (CASCADE)

HasMany

1:N relationship - One Entity owns multiple other Entities.

Basic Usage

user.entity.json

{
  "id": "User",
  "props": [
    {
      "type": "relation",
      "name": "posts",
      "with": "Post",
      "relationType": "HasMany",
      "joinColumn": "user_id",
      "desc": "Written posts"
    }
  ]
}

Requirements:

Post Entity must have a user_id column
Usually defined with BelongsToOne in reverse on Post

Options

Option	Type	Description	Default
`joinColumn`	string	FK column name in the other table	required
`fromColumn`	string	Reference column name in current table	`id`
`nullable`	boolean	Nullable for the relation itself (optional)	`false`

Example: Using fromColumn

{
  "type": "relation",
  "name": "childPosts",
  "with": "Post",
  "relationType": "HasMany",
  "joinColumn": "parent_post_id",
  "fromColumn": "id",
  "desc": "Child posts"
}

JOIN query:

SELECT * FROM posts
WHERE posts.parent_post_id = {user.id}

TypeScript Usage

{
  "subsets": {
    "A": [
      "id",
      "username",
      "posts.id",
      "posts.title",
      "posts.created_at"
    ]
  }
}

HasMany is automatically optimized using the DataLoader pattern. N+1 query problems don’t occur.

ManyToMany

N:M relationship - Many-to-many relationship implemented through a join table.

Basic Usage

post.entity.json

{
  "id": "Post",
  "props": [
    {
      "type": "relation",
      "name": "tags",
      "with": "Tag",
      "relationType": "ManyToMany",
      "joinTable": "posts__tags",
      "onUpdate": "CASCADE",
      "onDelete": "CASCADE",
      "desc": "Tags"
    }
  ]
}

Auto-generated Join Table:

CREATE TABLE posts__tags (
  id INTEGER PRIMARY KEY,
  post_id INTEGER NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
  tag_id INTEGER NOT NULL REFERENCES tags(id) ON DELETE CASCADE,
  UNIQUE(post_id, tag_id)
);

Options

Option	Type	Description	Default
`joinTable`	string	Join table name (`{table1}__${table2}`)	required
`onUpdate`	RelationOn	Action on referenced record update	required
`onDelete`	RelationOn	Action on referenced record delete	required
`nullable`	boolean	Nullable for the relation itself (optional)	`false`

Join Table Naming Convention: Sort two table names alphabetically and connect with __.

Correct: posts__tags
Wrong: tags__posts (not alphabetical order)

Bidirectional Definition

{
  "type": "relation",
  "name": "tags",
  "with": "Tag",
  "relationType": "ManyToMany",
  "joinTable": "posts__tags",
  "onUpdate": "CASCADE",
  "onDelete": "CASCADE"
}

TypeScript Usage

{
  "subsets": {
    "A": [
      "id",
      "title",
      "tags.id",
      "tags.name"
    ]
  }
}

Custom Join Clause

You can write SQL expressions directly when complex JOIN conditions are needed.

{
  "type": "relation",
  "name": "latestPost",
  "with": "Post",
  "relationType": "OneToOne",
  "hasJoinColumn": false,
  "customJoinClause": "users.id = posts.user_id AND posts.is_published = true",
  "desc": "Latest published post"
}

customJoinClause is an advanced feature. Use standard Relations when possible.

Relation Usage Patterns

1. Selecting Relation Fields in Subsets

{
  "subsets": {
    "A": [
      "id",
      "title",
      "user.username",
      "user.email",
      "tags.name"
    ]
  }
}

Auto-generated queries:

user: LEFT JOIN
tags: Separate query via DataLoader

2. Nested Relations

{
  "subsets": {
    "A": [
      "id",
      "title",
      "user.id",
      "user.username",
      "user.employee.department.name"
    ]
  }
}

Sonamu automatically generates the necessary JOINs:

FROM posts
LEFT JOIN users ON posts.user_id = users.id
LEFT JOIN employees ON users.id = employees.user_id
LEFT JOIN departments ON employees.department_id = departments.id

3. Filtering Relations

const posts = await this.puri()
  .where("user.role", "admin")
  .many();

4. Sorting by Relations

const posts = await this.puri()
  .orderBy("user.username", "asc")
  .many();

Relation Design Guide

BelongsToOne vs OneToOne

Situation	Recommended Type	Reason
Post → Author	`BelongsToOne`	Multiple posts belong to one user
User ↔ Profile	`OneToOne`	1:1 matching relationship
Order → Customer	`BelongsToOne`	Multiple orders belong to one customer

CASCADE vs RESTRICT

Situation	Recommended Action	Reason
User delete → Posts	`CASCADE`	Delete together
Category delete → Posts	`RESTRICT`	Cannot delete if posts exist
Department delete → Employees	`SET NULL`	Keep employees, set department to NULL

nullable Setting

Situation	nullable	Reason
Required relationship	`false`	Reference always needed
Optional relationship	`true`	May not exist
Temporary state	`true`	Set later

Cautions

Avoid Circular ReferencesAvoid circular references like A → B → C → A. This can cause problems when creating data.

JOIN Depth LimitToo deep nested Relations (3+ levels) can cause performance issues. Separate into different queries when needed.

ManyToMany Join TableSonamu automatically manages Join Tables, so you don’t need to create a separate Entity. Only separate into an Entity when additional columns are needed.

Next Steps

Enums

Define and use Enum types

Subset

Type-safe queries with Subsets

Puri Query Builder

Write queries using Relations

Performance

Optimize Relation queries

Get Started

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Troubleshooting

FAQ

​Relation Types Overview

BelongsToOne

OneToOne

HasMany

ManyToMany

​BelongsToOne

​Basic Usage

​Options

​RelationOn Options

​Example: nullable and CASCADE

​TypeScript Usage

​OneToOne

​Basic Usage

​Options

​Example: Bidirectional OneToOne

​HasMany

​Basic Usage

​Options

​Example: Using fromColumn

​TypeScript Usage

​ManyToMany

​Basic Usage

​Options

​Bidirectional Definition

​TypeScript Usage

​Custom Join Clause

​Relation Usage Patterns

​1. Selecting Relation Fields in Subsets

​2. Nested Relations

​3. Filtering Relations

​4. Sorting by Relations

​Relation Design Guide

​BelongsToOne vs OneToOne

​CASCADE vs RESTRICT

​nullable Setting

​Cautions

​Next Steps

Enums

Subset

Puri Query Builder

Performance

Relation Types Overview

BelongsToOne

Basic Usage

Options

RelationOn Options

Example: nullable and CASCADE

TypeScript Usage

OneToOne

Basic Usage

Options

Example: Bidirectional OneToOne

HasMany

Basic Usage

Options

Example: Using fromColumn

TypeScript Usage

ManyToMany

Basic Usage

Options

Bidirectional Definition

TypeScript Usage

Custom Join Clause

Relation Usage Patterns

1. Selecting Relation Fields in Subsets

2. Nested Relations

3. Filtering Relations

4. Sorting by Relations

Relation Design Guide

BelongsToOne vs OneToOne

CASCADE vs RESTRICT

nullable Setting

Cautions

Next Steps