Querying the database
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.
If you're building a REST API, you can use Prisma Client in your route handlers to read and write data in the database based on incoming HTTP requests. If you're building a GraphQL API, you can use Prisma Client in your resolvers to read and write data in the database based on incoming queries and mutations.
For the purpose of this guide however, you'll just create a plain Node.js script to learn how to send queries to your database using Prisma Client. Once you have an understanding of how the API works, you can start integrating it into your actual application code (e.g. REST route handlers or GraphQL resolvers).
Create a new file named index.ts
and add the following code to it:
import { PrismaClient } from '@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)
})
Here's a quick overview of the different parts of the code snippet:
- Import the
PrismaClient
constructor from the@prisma/client
node module - Instantiate
PrismaClient
- Define an
async
function namedmain
to send queries to the database - Connect to the database
- Call the
main
function - 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:
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 ts-node index.ts
If you introspected an existing database with records, the query should return an array of JavaScript objects.
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:
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 ts-node index.ts
The output should look similar to this:
[
{
id: '60cc9b0e001e3bfd00a6eddf',
email: 'hello@prisma.com',
name: 'Rich',
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
collections:
The id
field in the Prisma schema maps to _id
in the underlying MongoDB database.
User collection
_id | name | |
---|---|---|
60cc9b0e001e3bfd00a6eddf | "hello@prisma.com" | "Rich" |
Post collection
_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 identifier in the
authorId
document field onPost
reference the_id
document field in theUser
collection, meaning the_id
value60cc9b0e001e3bfd00a6eddf
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:
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 ts-node 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 🚀