Querying the database

TypeScript

MongoDB

Write your first query with Prisma Client

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.

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

index.ts

import { PrismaClient } from '@prisma/client'

const prisma = new PrismaClient()

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

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

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

1. Import the PrismaClient constructor from the @prisma/client node module
2. Instantiate PrismaClient
3. Define an async function named main to send queries to the database
4. Connect to the database
5. Call the main function
6. Close the database connections when the script terminates

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

index.ts

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

Now run the code with this command:

npx tsx index.ts

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

[]

Write data into the database

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.

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

index.ts

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 })
}

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.

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

Run the code with this command:

npx tsx index.ts

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',
      },
    ],
  },
]

Also note that allUsers is statically typed thanks to Prisma Client's generated types. You can observe the type by hovering over the allUsers variable in your editor. It should be typed as follows:

const allUsers: (User & {
  posts: Post[]
})[]

export type Post = {
  id: number
  title: string
  body: string | null
  published: boolean
  authorId: number | null
}

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

User

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

Post

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

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.

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.ts

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 })
}

Now run the code using the same command as before:

npx tsx index.ts

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!",
      },
    ],
  },
]

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