一对一的关系

本页介绍一对一关系并解释如何在 Prisma 模式中使用它们。

¥This page introduces one-to-one relations and explains how to use them in your Prisma schema.

Questions answered in this page

如何建模一对一关系？

¥How do I model one-to-one relations?
哪一方应该存储外键？

¥Which side should store the foreign key?
可选 1-1 与必需 1-n 之间如何工作？

¥How do optional vs required 1-1 work?

概述

¥Overview

一对一（1-1）关系是指关系两侧最多可以连接一条记录的关系。在下面的示例中，User 和 Profile 之间存在一对一的关系：

¥One-to-one (1-1) relations refer to relations where at most one record can be connected on both sides of the relation. In the example below, there is a one-to-one relation between User and Profile:

Relational databases

MongoDB

model User {
  id      Int      @id @default(autoincrement())
  profile Profile?
}

model Profile {
  id     Int  @id @default(autoincrement())
  user   User @relation(fields: [userId], references: [id])
  userId Int  @unique // relation scalar field (used in the `@relation` attribute above)
}

model User {
  id      String   @id @default(auto()) @map("_id") @db.ObjectId
  profile Profile?
}

model Profile {
  id     String @id @default(auto()) @map("_id") @db.ObjectId
  user   User   @relation(fields: [userId], references: [id])
  userId String @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

userId 关系标量是底层数据库中外键的直接表示。这种一对一的关系表达如下：

¥The userId relation scalar is a direct representation of the foreign key in the underlying database. This one-to-one relation expresses the following:

"一名用户可以有零个配置文件或一个配置文件"（因为 profile 字段是 User 上的 optional）

¥"a user can have zero profiles or one profile" (because the profile field is optional on User)
"一个配置文件必须始终连接到一个用户"

¥"a profile must always be connected to one user"

在前面的示例中，Profile 模型的 user 关系字段引用了 User 模型的 id 字段。你还可以引用不同的字段。在这种情况下，你需要使用 @unique 属性来标记该字段，以保证每个 Profile 上只有一个 User 连接。在以下示例中，user 字段引用 User 模型中的 email 字段，该字段用 @unique 属性标记：

¥In the previous example, the user relation field of the Profile model references the id field of the User model. You can also reference a different field. In this case, you need to mark the field with the @unique attribute, to guarantee that there is only a single User connected to each Profile. In the following example, the user field references an email field in the User model, which is marked with the @unique attribute:

Relational databases

MongoDB

model User {
  id      Int      @id @default(autoincrement())
  email   String   @unique // <-- add unique attribute
  profile Profile?
}

model Profile {
  id        Int    @id @default(autoincrement())
  user      User   @relation(fields: [userEmail], references: [email])
  userEmail String @unique // relation scalar field (used in the `@relation` attribute above)
}

model User {
  id      String   @id @default(auto()) @map("_id") @db.ObjectId
  email   String   @unique // <-- add unique attribute
  profile Profile?
}

model Profile {
  id        String @id @default(auto()) @map("_id") @db.ObjectId
  user      User   @relation(fields: [userEmail], references: [email])
  userEmail String @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

warning

在 MySQL 中，你可以创建仅在引用端有索引且没有唯一约束的外键。在 Prisma ORM 版本 4.0.0 及更高版本中，如果你内省这种类型的关系，它将触发验证错误。要解决此问题，你需要向引用的字段添加 @unique 约束。

¥In MySQL, you can create a foreign key with only an index on the referenced side, and not a unique constraint. In Prisma ORM versions 4.0.0 and later, if you introspect a relation of this type it will trigger a validation error. To fix this, you will need to add a @unique constraint to the referenced field.

关系数据库中的多字段关系

¥Multi-field relations in relational databases

仅在关系数据库中，你还可以使用多字段 ID 定义 1-1 关系：

¥In relational databases only, you can also use multi-field IDs to define a 1-1 relation:

model User {
  firstName String
  lastName  String
  profile   Profile?

  @@id([firstName, lastName])
}

model Profile {
  id            Int    @id @default(autoincrement())
  user          User   @relation(fields: [userFirstName, userLastName], references: [firstName, lastName])
  userFirstName String // relation scalar field (used in the `@relation` attribute above)
  userLastName  String // relation scalar field (used in the `@relation` attribute above)

  @@unique([userFirstName, userLastName])
}

数据库中的 1-1 关系

¥1-1 relations in the database

关系数据库

¥Relational databases

以下示例演示如何在 SQL 中创建 1-1 关系：

¥The following example demonstrates how to create a 1-1 relation in SQL:

CREATE TABLE "User" (
    id SERIAL PRIMARY KEY
);
CREATE TABLE "Profile" (
    id SERIAL PRIMARY KEY,
    "userId" INTEGER NOT NULL UNIQUE,
    FOREIGN KEY ("userId") REFERENCES "User"(id)
);

请注意，外键 userId 存在 UNIQUE 约束。如果缺少此 UNIQUE 约束，则该关系将被视为 1-n 关系。

¥Notice that there is a UNIQUE constraint on the foreign key userId. If this UNIQUE constraint was missing, the relation would be considered a 1-n relation.

以下示例演示如何使用组合键（firstName 和 lastName）在 SQL 中创建 1-1 关系：

¥The following example demonstrates how to create a 1-1 relation in SQL using a composite key (firstName and lastName):

CREATE TABLE "User" (
    firstName TEXT,
    lastName TEXT,
    PRIMARY KEY ("firstName","lastName")
);
CREATE TABLE "Profile" (
    id SERIAL PRIMARY KEY,
    "userFirstName" TEXT NOT NULL,
    "userLastName" TEXT NOT NULL,
    UNIQUE ("userFirstName", "userLastName")
    FOREIGN KEY ("userFirstName", "userLastName") REFERENCES "User"("firstName", "lastName")
);

MongoDB

对于 MongoDB，Prisma ORM 目前使用规范化数据模型设计，这意味着文档以与关系数据库类似的方式通过 ID 相互引用。

¥For MongoDB, Prisma ORM currently uses a normalized data model design, which means that documents reference each other by ID in a similar way to relational databases.

以下 MongoDB 文档代表 User：

¥The following MongoDB document represents a User:

{ "_id": { "$oid": "60d58e130011041800d209e1" }, "name": "Bob" }

以下 MongoDB 文档代表 Profile - 注意 userId 字段，它引用 User 文档的 $oid：

¥The following MongoDB document represents a Profile - notice the userId field, which references the User document's $oid:

{
  "_id": { "$oid": "60d58e140011041800d209e2" },
  "bio": "I'm Bob, and I like drawing.",
  "userId": { "$oid": "60d58e130011041800d209e1" }
}

必填和可选 1-1 关系字段

¥Required and optional 1-1 relation fields

在一对一关系中，没有关系标量的关系一侧（表示数据库中外键的字段）必须是可选的：

¥In a one-to-one relation, the side of the relation without a relation scalar (the field representing the foreign key in the database) must be optional:

model User {
  id      Int      @id @default(autoincrement())
  profile Profile? // No relation scalar - must be optional
}

此限制是在 2.12.0 中引入的。

¥This restriction was introduced in 2.12.0.

但是，你可以选择带有关系标量的关系的一侧是可选的还是强制的。

¥However, you can choose if the side of the relation with a relation scalar should be optional or mandatory.

强制 1-1 关系

¥Mandatory 1-1 relation

在以下示例中，profile 和 profileId 为必填项。这意味着你无法在不连接或创建 Profile 的情况下创建 User：

¥In the following example, profile and profileId are mandatory. This means that you cannot create a User without connecting or creating a Profile:

model User {
  id        Int     @id @default(autoincrement())
  profile   Profile @relation(fields: [profileId], references: [id]) // references `id` of `Profile`
  profileId Int     @unique // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   Int   @id @default(autoincrement())
  user User?
}

可选的 1-1 关系

¥Optional 1-1 relation

在以下示例中，profile 和 profileId 是可选的。这意味着你可以创建用户而无需连接或创建 Profile：

¥In the following example, profile and profileId are optional. This means that you can create a user without connecting or creating a Profile:

model User {
  id        Int      @id @default(autoincrement())
  profile   Profile? @relation(fields: [profileId], references: [id]) // references `id` of `Profile`
  profileId Int?     @unique // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   Int   @id @default(autoincrement())
  user User?
}

选择哪一方应以 1-1 关系存储外键

¥Choosing which side should store the foreign key in a 1-1 relation

在 1-1 关系中，你可以自己决定要使用 @relation 属性注释关系的哪一侧（因此保留外键）。

¥In 1-1 relations, you can decide yourself which side of the relation you want to annotate with the @relation attribute (and therefore holds the foreign key).

在以下示例中，Profile 模型上的关系字段使用 @relation 属性进行注释。userId 是底层数据库中外键的直接表示：

¥In the following example, the relation field on the Profile model is annotated with the @relation attribute. userId is a direct representation of the foreign key in the underlying database:

Relational databases

MongoDB

model User {
  id      Int      @id @default(autoincrement())
  profile Profile?
}

model Profile {
  id     Int  @id @default(autoincrement())
  user   User @relation(fields: [userId], references: [id])
  userId Int  @unique // relation scalar field (used in the `@relation` attribute above)
}

model User {
  id      String   @id @default(auto()) @map("_id") @db.ObjectId
  profile Profile?
}

model Profile {
  id     String @id @default(auto()) @map("_id") @db.ObjectId
  user   User   @relation(fields: [userId], references: [id])
  userId String @unique @db.ObjectId
}

你还可以使用 @relation 属性注释关系的另一端。以下示例注释了 User 模型上的关系字段。profileId 是底层数据库中外键的直接表示：

¥You can also annotate the other side of the relation with the @relation attribute. The following example annotates the relation field on the User model. profileId is a direct representation of the foreign key in the underlying database:

Relational databases

MongoDB

model User {
  id        Int      @id @default(autoincrement())
  profile   Profile? @relation(fields: [profileId], references: [id])
  profileId Int?     @unique // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   Int   @id @default(autoincrement())
  user User?
}

model User {
  id        String   @id @default(auto()) @map("_id") @db.ObjectId
  profile   Profile? @relation(fields: [profileId], references: [id])
  profileId String?  @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   String @id @default(auto()) @map("_id") @db.ObjectId
  user User?
}

概述​

关系数据库中的多字段关系​

数据库中的 1-1 关系​

关系数据库​

MongoDB​

必填和可选 1-1 关系字段​

强制 1-1 关系​

可选的 1-1 关系​

选择哪一方应以 1-1 关系存储外键​

概述

关系数据库中的多字段关系

数据库中的 1-1 关系

关系数据库

MongoDB

必填和可选 1-1 关系字段

强制 1-1 关系

可选的 1-1 关系

选择哪一方应以 1-1 关系存储外键