在 Typescript 项目中改进 MySQL 数据库的架构

将 `Tag` 模型添加到你的架构中

¥Add a Tag model to your schema

在本部分中，你将发展 Prisma 架构，然后使用 prisma migrate dev 生成迁移并将其应用到数据库。

¥In this section, you will evolve your Prisma schema and then generate and apply the migration to your database with prisma migrate dev.

出于本指南的目的，我们将对 Prisma 架构进行以下更改：

¥For the purpose of this guide, we'll make the following changes to the Prisma schema:

创建一个名为 Tag 的新模型，其中包含以下字段：

¥Create a new model called Tag with the following fields:
- id：将作为模型主键的自动递增整数
  
  ¥id: an auto-incrementing integer that will be the primary key for the model
- name：非空 String
  
  ¥name: a non-null String
- posts：链接到 Post 模型的隐式多对多关系字段
  
  ¥posts: an implicit many-to-many relation field that links to the Post model
使用链接到 Tag 模型的隐式多对多关系字段的 tags 字段更新 Post 模型

¥Update the Post model with a tags field with an implicit many-to-many relation field that links to the Tag model

对架构进行更改后，你的架构应类似于以下架构：

¥Once you've made the changes to your schema, your schema should resemble the one below:

prisma/schema.prisma

model Post {
  id        Int      @id @default(autoincrement())
  title     String   @db.VarChar(255)
  createdAt DateTime @default(now()) @db.Timestamp(6)
  content   String?
  published Boolean  @default(false)
  authorId  Int
  user      User     @relation(fields: [authorId], references: [id])
  tags      Tag[]
}

model Profile {
  id     Int     @id @default(autoincrement())
  bio    String?
  userId Int     @unique
  user   User    @relation(fields: [userId], references: [id])
}

model User {
  id      Int      @id @default(autoincrement())
  name    String?  @db.VarChar(255)
  email   String   @unique @db.VarChar(255)
  post    Post[]
  profile Profile?
}

model Tag {
  id    Int    @id @default(autoincrement())
  name  String
  posts Post[]
}

要将 Prisma 架构更改应用到数据库，请使用 prisma migrate dev CLI 命令：

¥To apply your Prisma schema changes to your database, use the prisma migrate dev CLI command:

npx prisma migrate dev --name tags-model

该命令将：

¥This command will:

为迁移创建新的 SQL 迁移文件

¥Create a new SQL migration file for the migration
将生成的 SQL 迁移应用到数据库

¥Apply the generated SQL migration to the database
重新生成 Prisma 客户端

¥Regenerate Prisma Client

将生成以下迁移并保存在你的 prisma/migrations 文件夹中：

¥The following migration will be generated and saved in your prisma/migrations folder:

prisma/migrations/TIMESTAMP_tags_model.sql

-- CreateTable
CREATE TABLE Tag (
    id SERIAL NOT NULL,
    name VARCHAR(255) NOT NULL,

    CONSTRAINT Tag_pkey PRIMARY KEY (id)
);

-- CreateTable
CREATE TABLE _PostToTag (
    A INTEGER NOT NULL,
    B INTEGER NOT NULL
);

-- CreateIndex
CREATE UNIQUE INDEX _PostToTag_AB_unique ON _PostToTag(A, B);

-- CreateIndex
CREATE INDEX _PostToTag_B_index ON _PostToTag(B);

-- AddForeignKey
ALTER TABLE _PostToTag ADD CONSTRAINT _PostToTag_A_fkey FOREIGN KEY (A) REFERENCES Post(id) ON DELETE CASCADE ON UPDATE CASCADE;

-- AddForeignKey
ALTER TABLE _PostToTag ADD CONSTRAINT _PostToTag_B_fkey FOREIGN KEY (B) REFERENCES Tag(id) ON DELETE CASCADE ON UPDATE CASCADE;

恭喜，你刚刚使用 Prisma Migrate 改进了数据库 🚀

¥Congratulations, you just evolved your database with Prisma Migrate 🚀

将 Tag 模型添加到你的架构中​

将 `Tag` 模型添加到你的架构中