Relation queries
A key feature of Prisma Client is the ability to query relations between two or more models. Relation queries include:
- Nested reads (sometimes referred to as eager loading) via
select
andinclude
- Nested writes with transactional guarantees
- Filtering on related records
Prisma Client also has a fluent API for traversing relations.
Nested reads
Nested reads allow you to read related data from multiple tables in your database - such as a user and that user's posts. You can:
- Use
include
to include related records, such as a user's posts or profile, in the query response. - Use a nested
select
to include specific fields from a related record. You can also nestselect
inside aninclude
.
Relation load strategies (Preview)
Since version 5.8.0, you can decide on a per-query-level how you want Prisma Client to execute a relation query (i.e. what load strategy should be applied) via the relationLoadStrategy
option for PostgreSQL databases.
Since version 5.10.0, this feature is also available for MySQL.
Because the relationLoadStrategy
option is currently in Preview, you need to enable it via the relationJoins
preview feature flag in your Prisma schema file:
generator client {
provider = "prisma-client-js"
previewFeatures = ["relationJoins"]
}
After adding this flag, you need to run prisma generate
again to re-generate Prisma Client. This feature is currently available on PostgreSQL, CockroachDB and MySQL.
Prisma Client supports two load strategies for relations:
join
(default): Uses a database-levelLATERAL JOIN
(PostgreSQL) or correlated subqueries (MySQL) and fetches all data with a single query to the database.query
: Sends multiple queries to the database (one per table) and joins them on the application level.
Another important difference between these two options is that the join
strategy uses JSON aggregation on the database level. That means that it creates the JSON structures returned by Prisma Client already in the database which saves computation resources on the application level.
Note: Once
relationLoadStrategy
moves from Preview into General Availability,join
will universally become the default for all relation queries.
Examples
You can use the relationLoadStrategy
option on the top-level in any query that supports include
or select
.
Here is an example with include
:
const users = await prisma.user.findMany({
relationLoadStrategy: 'join', // or 'query'
include: {
posts: true,
},
})
And here is another example with select
:
const users = await prisma.user.findMany({
relationLoadStrategy: 'join', // or 'query'
select: {
posts: true,
},
})
When to use which load strategy?
- The
join
strategy (default) will be more effective in most scenarios. On PostgreSQL, it uses a combination ofLATERAL JOINs
and JSON aggregation to reduce redundancy in result sets and delegate the work of transforming the query results into the expected JSON structures on the database server. On MySQL, it uses correlated subqueries to fetch the results with a single query. - There may be edge cases where
query
could be more performant depending on the characteristics of the dataset and query. We recommend that you profile your database queries to identify these situations. - Use
query
if you want to save resources on the database server and do heavy-lifting of merging and transforming data in the application server which might be easier to scale.
Include a relation
The following example returns a single user and that user's posts:
const user = await prisma.user.findFirst({
include: {
posts: true,
},
})
Include all fields for a specific relation
The following example returns a post and its author:
const post = await prisma.post.findFirst({
include: {
author: true,
},
})
Include deeply nested relations
You can nest include
options to include relations of relations. The following example returns a user's posts, and each post's categories:
const user = await prisma.user.findFirst({
include: {
posts: {
include: {
categories: true,
},
},
},
})
Select specific fields of included relations
You can use a nested select
to choose a subset of fields of relations to return. For example, the following query returns the user's name
and the title
of each related post:
const user = await prisma.user.findFirst({
select: {
name: true,
posts: {
select: {
title: true,
},
},
},
})
You can also nest a select
inside an include
- the following example returns all User
fields and the title
field of each post:
const user = await prisma.user.findFirst({
include: {
posts: {
select: {
title: true,
},
},
},
})
Note that you cannot use select
and include
on the same level. This means that if you choose to include
a user's post and select
each post's title, you cannot select
only the users' email
:
// The following query returns an exception
const user = await prisma.user.findFirst({
select: { // This won't work!
email: true
}
include: { // This won't work!
posts: {
select: {
title: true
}
}
},
})
Instead, use nested select
options:
const user = await prisma.user.findFirst({
select: {
// This will work!
email: true,
posts: {
select: {
title: true,
},
},
},
})
Relation count
In 3.0.1 and later, you can include
or select
a count of relations alongside fields - for example, a user's post count.
const relationCount = await prisma.user.findMany({
include: {
_count: {
select: { posts: true },
},
},
})
Filter a list of relations
When you use select
or include
to return a subset of the related data, you can filter and sort the list of relations inside the select
or include
.
For example, the following query returns all users and a list of titles of the unpublished posts associated with each user:
const result = await prisma.user.findFirst({
select: {
posts: {
where: {
published: false,
},
orderBy: {
title: 'asc',
},
select: {
title: true,
},
},
},
})
You can also write the same query using include
as follows:
const result = await prisma.user.findFirst({
include: {
posts: {
where: {
published: false,
},
orderBy: {
title: 'asc',
},
},
},
})
Nested writes
A nested write allows you to write relational data to your database in a single transaction.
Nested writes:
- Provide transactional guarantees for creating, updating or deleting data across multiple tables in a single Prisma Client query. If any part of the query fails (for example, creating a user succeeds but creating posts fails), Prisma Client rolls back all changes.
- Support any level of nesting supported by the data model.
- Are available for relation fields when using the model's create or update query. The following section shows the nested write options that are available per query.
Create a related record
You can create a record and one or more related records at the same time. The following query creates a User
record and two related Post
records:
const result = await prisma.user.create({
data: {
email: 'elsa@prisma.io',
name: 'Elsa Prisma',
posts: {
create: [
{ title: 'How to make an omelette' },
{ title: 'How to eat an omelette' },
],
},
},
include: {
posts: true, // Include all posts in the returned object
},
})
Create a single record and multiple related records
There are two ways to create or update a single record and multiple related records - for example, a user with multiple posts:
- Use a nested
create
query - Use a nested
createMany
query
In most cases, a nested create
will be preferable unless the skipDuplicates
query option is required. Here's a quick table describing the differences between the two options:
Feature | create | createMany | Notes |
---|---|---|---|
Supports nesting additional relations | ✔ | ✘ * | For example, you can create a user, several posts, and several comments per post in one query. * You can manually set a foreign key in a has-one relation - for example: { authorId: 9} |
Supports 1-n relations | ✔ | ✔ | For example, you can create a user and multiple posts (one user has many posts) |
Supports m-n relations | ✔ | ✘ | For example, you can create a post and several categories (one post can have many categories, and one category can have many posts) |
Supports skipping duplicate records | ✘ | ✔ | Use skipDuplicates query option. |
Using nested create
The following query uses nested create
to create:
- One user
- Two posts
- One post category
The example also uses a nested include
to include all posts and post categories in the returned data.
const result = await prisma.user.create({
data: {
email: 'yvette@prisma.io',
name: 'Yvette',
posts: {
create: [
{
title: 'How to make an omelette',
categories: {
create: {
name: 'Easy cooking',
},
},
},
{ title: 'How to eat an omelette' },
],
},
},
include: {
// Include posts
posts: {
include: {
categories: true, // Include post categories
},
},
},
})
Using nested createMany
The following query uses a nested createMany
to create:
- One user
- Two posts
The example also uses a nested include
to include all posts in the returned data.
const result = await prisma.user.create({
data: {
email: 'saanvi@prisma.io',
posts: {
createMany: {
data: [{ title: 'My first post' }, { title: 'My second post' }],
},
},
},
include: {
posts: true,
},
})
Note: It is not possible to nest an additional create
or createMany
inside the highlighted query, which means that you cannot create a user, posts, and post categories at the same time.
Create multiple records and multiple related records
You cannot access relations in a createMany()
or createManyAndReturn()
query, which means that you cannot create multiple users and multiple posts in a single nested write. The following is not possible:
const createMany = await prisma.user.createMany({
data: [
{
name: 'Yewande',
email: 'yewande@prisma.io',
posts: {
// Not possible to create posts!
},
},
{
name: 'Noor',
email: 'noor@prisma.io',
posts: {
// Not possible to create posts!
},
},
],
})
Connect multiple records
The following query creates (create
) a new User
record and connects that record (connect
) to three existing posts:
const result = await prisma.user.create({
data: {
email: 'vlad@prisma.io',
posts: {
connect: [{ id: 8 }, { id: 9 }, { id: 10 }],
},
},
include: {
posts: true, // Include all posts in the returned object
},
})
Note: Prisma Client throws an exception if any of the post records cannot be found:
connect: [{ id: 8 }, { id: 9 }, { id: 10 }]
Connect a single record
You can connect
an existing record to a new or existing user. The following query connects an existing post (id: 11
) to an existing user (id: 9
)
const result = await prisma.user.update({
where: {
id: 9,
},
data: {
posts: {
connect: {
id: 11,
},
},
},
include: {
posts: true,
},
})
Connect or create a record
If a related record may or may not already exist, use connectOrCreate
to connect the related record:
- Connect a
User
with the email addressviola@prisma.io
or - Create a new
User
with the email addressviola@prisma.io
if the user does not already exist
const result = await prisma.post.create({
data: {
title: 'How to make croissants',
author: {
connectOrCreate: {
where: {
email: 'viola@prisma.io',
},
create: {
email: 'viola@prisma.io',
name: 'Viola',
},
},
},
},
include: {
author: true,
},
})
Disconnect a related record
To disconnect
one out of a list of records (for example, a specific blog post) provide the ID or unique identifier of the record(s) to disconnect:
const result = await prisma.user.update({
where: {
id: 16,
},
data: {
posts: {
disconnect: [{ id: 12 }, { id: 19 }],
},
},
include: {
posts: true,
},
})
To disconnect
one record (for example, a post's author), use disconnect: true
:
const result = await prisma.post.update({
where: {
id: 23,
},
data: {
author: {
disconnect: true,
},
},
include: {
author: true,
},
})
Disconnect all related records
To disconnect
all related records in a one-to-many relation (a user has many posts), set
the relation to an empty list as shown:
const result = await prisma.user.update({
where: {
id: 16,
},
data: {
posts: {
set: [],
},
},
include: {
posts: true,
},
})
Delete all related records
Delete all related Post
records:
const result = await prisma.user.update({
where: {
id: 11,
},
data: {
posts: {
deleteMany: {},
},
},
include: {
posts: true,
},
})
Delete specific related records
Update a user by deleting all unpublished posts:
const result = await prisma.user.update({
where: {
id: 11,
},
data: {
posts: {
deleteMany: {
published: false,
},
},
},
include: {
posts: true,
},
})
Update a user by deleting specific posts:
const result = await prisma.user.update({
where: {
id: 6,
},
data: {
posts: {
deleteMany: [{ id: 7 }],
},
},
include: {
posts: true,
},
})
Update all related records (or filter)
You can use a nested updateMany
to update all related records for a particular user. The following query unpublishes all posts for a specific user:
const result = await prisma.user.update({
where: {
id: 6,
},
data: {
posts: {
updateMany: {
where: {
published: true,
},
data: {
published: false,
},
},
},
},
include: {
posts: true,
},
})
Update a specific related record
const result = await prisma.user.update({
where: {
id: 6,
},
data: {
posts: {
update: {
where: {
id: 9,
},
data: {
title: 'My updated title',
},
},
},
},
include: {
posts: true,
},
})
Update or create a related record
The following query uses a nested upsert
to update "bob@prisma.io"
if that user exists, or create the user if they do not exist:
const result = await prisma.post.update({
where: {
id: 6,
},
data: {
author: {
upsert: {
create: {
email: 'bob@prisma.io',
name: 'Bob the New User',
},
update: {
email: 'bob@prisma.io',
name: 'Bob the existing user',
},
},
},
},
include: {
author: true,
},
})
Add new related records to an existing record
You can nest create
or createMany
inside an update
to add new related records to an existing record. The following query adds two posts to a user with an id
of 9:
const result = await prisma.user.update({
where: {
id: 9,
},
data: {
posts: {
createMany: {
data: [{ title: 'My first post' }, { title: 'My second post' }],
},
},
},
include: {
posts: true,
},
})
Relation filters
Filter on "-to-many" relations
Prisma Client provides the some
, every
, and none
options to filter records by the properties of related records on the "-to-many" side of the relation. For example, filtering users based on properties of their posts.
For example:
Requirement | Query option to use |
---|---|
"I want a list of every User that has at least one unpublished Post record" | some posts are unpublished |
"I want a list of every User that has no unpublished Post records" | none of the posts are unpublished |
"I want a list of every User that has only unpublished Post records" | every post is unpublished |
For example, the following query returns User
that meet the following criteria:
- No posts with more than 100 views
- All posts have less than, or equal to 50 likes
const users = await prisma.user.findMany({
where: {
posts: {
none: {
views: {
gt: 100,
},
},
every: {
likes: {
lte: 50,
},
},
},
},
include: {
posts: true,
},
})
Filter on "-to-one" relations
Prisma Client provides the is
and isNot
options to filter records by the properties of related records on the "-to-one" side of the relation. For example, filtering posts based on properties of their author.
For example, the following query returns Post
records that meet the following criteria:
- Author's name is not Bob
- Author is older than 40
const users = await prisma.post.findMany({
where: {
author: {
isNot: {
name: 'Bob',
},
is: {
age: {
gt: 40,
},
},
},
},
include: {
author: true,
},
})
Filter on absence of "-to-many" records
For example, the following query uses none
to return all users that have zero posts:
const usersWithZeroPosts = await prisma.user.findMany({
where: {
posts: {
none: {},
},
},
include: {
posts: true,
},
})
Filter on absence of "-to-one" relations
The following query returns all posts that don't have an author relation:
const postsWithNoAuthor = await prisma.post.findMany({
where: {
author: null, // or author: { }
},
include: {
author: true,
},
})
Filter on presence of related records
The following query returns all users with at least one post:
const usersWithSomePosts = await prisma.user.findMany({
where: {
posts: {
some: {},
},
},
include: {
posts: true,
},
})
Fluent API
The fluent API lets you fluently traverse the relations of your models via function calls. Note that the last function call determines the return type of the entire query (the respective type annotations are added in the code snippets below to make that explicit).
This query returns all Post
records by a specific User
:
const postsByUser: Post[] = await prisma.user
.findUnique({ where: { email: 'alice@prisma.io' } })
.posts()
This is equivalent to the following findMany
query:
const postsByUser = await prisma.post.findMany({
where: {
author: {
email: 'alice@prisma.io',
},
},
})
The main difference between the queries is that the fluent API call is translated into two separate database queries while the other one only generates a single query (see this GitHub issue)
Note: You can use the fact that
.findUnique({ where: { email: 'alice@prisma.io' } }).posts()
queries are automatically batched by the Prisma dataloader in Prisma Client to avoid the n+1 problem in GraphQL resolvers.
This request returns all categories by a specific post:
const categoriesOfPost: Category[] = await prisma.post
.findUnique({ where: { id: 1 } })
.categories()
Note that you can chain as many queries as you like. In this example, the chaining starts at Profile
and goes over User
to Post
:
const posts: Post[] = await prisma.profile
.findUnique({ where: { id: 1 } })
.user()
.posts()
The only requirement for chaining is that the previous function call must return only a single object (e.g. as returned by a findUnique
query or a "to-one relation" like profile.user()
).
The following query is not possible because findMany
does not return a single object but a list:
// This query is illegal
const posts = await prisma.user.findMany().posts()