使用 JavaScript 和 MongoDB 查询数据库

JavaScript

MongoDB

使用 Prisma 客户端编写你的第一个查询

¥Write your first query with Prisma Client

现在你已经生成了 Prisma 客户端，你可以开始编写查询以在数据库中读取和写入数据。出于本指南的目的，你将使用简单的 Node.js 脚本来探索 Prisma Client 的一些基本功能。

¥Now that you have generated Prisma Client, you can start writing queries to read and write data in your database. For the purpose of this guide, you'll use a plain Node.js script to explore some basic features of Prisma Client.

创建一个名为 index.js 的新文件并添加以下代码：

¥Create a new file named index.js and add the following code to it:

index.js

const { PrismaClient } = require('@prisma/client')

const prisma = new PrismaClient()

async function main() {
  // ... you will write your Prisma Client queries here
}

main()
  .then(async () => {
    await prisma.$disconnect()
  })
  .catch(async (e) => {
    console.error(e)
    await prisma.$disconnect()
    process.exit(1)
  })

以下是代码片段不同部分的快速概述：

¥Here's a quick overview of the different parts of the code snippet:

1. 从 @prisma/client 节点模块导入 PrismaClient 构造函数

   ¥Import the PrismaClient constructor from the @prisma/client node module

2. 实例化 PrismaClient

   ¥Instantiate PrismaClient

3. 定义一个名为 main 的 async 函数来向数据库发送查询

   ¥Define an async function named main to send queries to the database

4. 连接到数据库

   ¥Connect to the database

5. 调用 main 函数

   ¥Call the main function

6. 脚本终止时关闭数据库连接

   ¥Close the database connections when the script terminates

在 main 函数中，添加以下查询以从数据库读取所有 User 记录并打印结果：

¥Inside the main function, add the following query to read all User records from the database and print the result:

index.js

async function main() {
-  // ... you will write your Prisma Client queries here
+  const allUsers = await prisma.user.findMany()
+  console.log(allUsers)
}

现在使用以下命令运行代码：

¥Now run the code with this command:

node index.js

这应该打印一个空数组，因为数据库中还没有 User 记录：

¥This should print an empty array because there are no User records in the database yet:

[]

将数据写入数据库

¥Write data into the database

你在上一节中使用的 findMany 查询仅从数据库中读取数据（尽管它仍然是空的）。在本节中，你将学习如何编写查询以将新记录写入 Post、User 和 Comment 表中。

¥The findMany query you used in the previous section only reads data from the database (although it was still empty). In this section, you'll learn how to write a query to write new records into the Post, User and Comment tables.

调整 main 函数以向数据库发送 create 查询：

¥Adjust the main function to send a create query to the database:

index.js

async function main() {
  await prisma.user.create({
    data: {
      name: 'Rich',
      email: 'hello@prisma.com',
      posts: {
        create: {
          title: 'My first post',
          body: 'Lots of really interesting stuff',
          slug: 'my-first-post',
        },
      },
    },
  })

  const allUsers = await prisma.user.findMany({
    include: {
      posts: true,
    },
  })
  console.dir(allUsers, { depth: null })
}

此代码使用 嵌套写入 查询创建一条新的 User 记录以及一条新的 Post。User 记录分别通过 Post.author ↔ User.posts 关系字段 连接到另一条记录。

¥This code creates a new User record together with a new Post using a nested write query. The User record is connected to the other one via the Post.author ↔ User.posts relation fields respectively.

请注意，你将 include 选项传递给 findMany，这告诉 Prisma 客户端在返回的 User 对象上包含 posts 关系。

¥Notice that you're passing the include option to findMany which tells Prisma Client to include the posts relations on the returned User objects.

使用以下命令运行代码：

¥Run the code with this command:

node index.js

输出应类似于以下内容：

¥The output should look similar to this:

[
  {
    id: '60cc9b0e001e3bfd00a6eddf',
    email: 'hello@prisma.com',
    name: 'Rich',
    address: null,
    posts: [
      {
        id: '60cc9bad005059d6007f45dd',
        slug: 'my-first-post',
        title: 'My first post',
        body: 'Lots of really interesting stuff',
        userId: '60cc9b0e001e3bfd00a6eddf',
      },
    ],
  },
]

该查询将新记录添加到 User 和 Post 表中：

¥The query added new records to the User and the Post tables:

用户

¥User

id	email	name
60cc9b0e001e3bfd00a6eddf	"hello@prisma.com"	"Rich"

邮政

¥Post

id	createdAt	title	content	published	authorId
60cc9bad005059d6007f45dd	2020-03-21T16:45:01.246Z	"My first post"	Lots of really interesting stuff	false	60cc9b0e001e3bfd00a6eddf

注意：Post 上的 authorId 列中的唯一 ID 引用 User 表的 id 列，这意味着 id 值 60cc9b0e001e3bfd00a6eddf 列因此引用数据库中的第一条（也是唯一一条）User 记录。

¥Note: The unique IDs in the authorId column on Post reference the id column of the User table, meaning the id value 60cc9b0e001e3bfd00a6eddf column therefore refers to the first (and only) User record in the database.

在继续下一部分之前，你将向刚刚使用 update 查询创建的 Post 记录添加一些注释。调整 main 功能如下：

¥Before moving on to the next section, you'll add a couple of comments to the Post record you just created using an update query. Adjust the main function as follows:

index.js

async function main() {
  await prisma.post.update({
    where: {
      slug: 'my-first-post',
    },
    data: {
      comments: {
        createMany: {
          data: [
            { comment: 'Great post!' },
            { comment: "Can't wait to read more!" },
          ],
        },
      },
    },
  })
  const posts = await prisma.post.findMany({
    include: {
      comments: true,
    },
  })

  console.dir(posts, { depth: Infinity })
}

现在使用与之前相同的命令运行代码：

¥Now run the code using the same command as before:

node index.js

你将看到以下输出：

¥You will see the following output:

[
  {
    id: '60cc9bad005059d6007f45dd',
    slug: 'my-first-post',
    title: 'My first post',
    body: 'Lots of really interesting stuff',
    userId: '60cc9b0e001e3bfd00a6eddf',
    comments: [
      {
        id: '60cca420008a21d800578793',
        postId: '60cca40300af8bf000f6ca99',
        comment: 'Great post!',
      },
      {
        id: '60cca420008a21d800578794',
        postId: '60cca40300af8bf000f6ca99',
        comment: "Can't wait to try this!",
      },
    ],
  },
]

太棒了，你刚刚使用 Prisma 客户端第一次将新数据写入数据库 🚀

¥Fantastic, you just wrote new data into your database for the first time using Prisma Client 🚀