Reading Data JAVASCRIPT Rsc2

import Collapse from "components/Markdown/Collapse" import Code from "components/Markdown/Code" import Warning from "components/Markdown/Warning" import Info from "components/Markdown/Info"

export const meta = { title: "Reading Data (JavaScript)", position: 50, technology: "node", technologyOrder: 1, articleGroup: "Reading Data", }

Overview

The Prisma client is based on the operations defined in the GraphQL schema of your Prisma API. For reading data, it basically mirrors the GraphQL queries of your Prisma service.

For this page, we'll assume your Prisma API is based on the following datamodel:

graphql

type Link {
  id: ID! @unique
  createdAt: DateTime!
  description: String!
  url: String!
  postedBy: User
  votes: [Vote!]!
}

type User {
  id: ID! @unique
  name: String!
  email: String! @unique
  password: String!
  links: [Link!]!
  votes: [Vote!]!
}

type Vote {
  id: ID! @unique
  link: Link!
  user: User!
}

You can view what the generated GraphQL schema for the API here
You can view what the generated JavaScript client here.

</Collapse>

Whenever a model is queried using the Prisma client, all scalar fields of that model are fetched. This is true no matter if a single object or a list of objects is queried.

For example, the following query returns all scalar fields of a single User:

const user = await prisma.user({ email: "[email protected]" })

In this case, the returned user object will have four properties (that correspond to the scalar fields of the User model): id, name, email and password.

The links and votes fields are both relation fields and are therefore not included in the query.

Here is an example of fetching a list of User objects:

const users = await prisma.users()

Similar to the previous query, each object inside the users array only has the scalar and no relation fields.

Fetching single objects

For each model type in your datamodel, there is a method generated in the Prisma client API that allows to fetch single objects of that model. The method is named after the type but starts with a lowercase character. For the sample datamodel from above, the three methods for fetching single User, Link and Vote objects are called user, link and vote.

The input for these functions is an object that has as properties any unique field of the model. This means, for all three methods, the id field is accepted (as the corresponding models each have an id field annotated as @unique). The input object for the user method additionaly has an email field.

View the type of where for Link here
View the type of where for User here
View the type of where for Vote here

</Collapse>

Examples

Fetch a single vote by its id:

const vote = await prisma.vote({ id: "cjlgpyueg001o0a239d3i07ao" })

graphql

# generated query
query {
  vote(where: {
    id: "cjlgpyueg001o0a239d3i07ao"
  }) {
    id
  }
}

</Code>

Fetch a single user by their email:

const user = await prisma.user({ email: "[email protected]" })

graphql

# generated query
query {
  user(where: {
    email: "[email protected]"
  }) {
    id
  }
}

</Code>

Fetching lists

For each model type in your datamodel, there is a method generated in the Prisma client API that allows to fetch a list of those model objects. The method is named after the model but starts with a lowercase character and uses the plural form. For the sample datamodel from above, the three methods for fetching lists of User, Link and Vote models are called users, links and votes.

The input arugment for these functions is an object that has properties for:

Filtering: where
Ordering: orderBy
Pagination: before, after, first, last, skip

Examples

Fetch all links:

const links = await prisma.links()

graphql

# generated query
query {
  links {
    id
    createdAt
    url
    description
  }
}

</Code>

Fetch a list of users:

const users = await prisma.users()

graphql

# generated query
query {
  users {
    id
    name
    email
    password
  }
}

</Code>

Relations

Prisma client has a fluent API to query relations in your data graph. Meaning you can simply chain your method calls to navigate the relation properties of the returned models.

This is only possible when retrieving single objects, not for lists. Meaning you can not query relation fields of objects that are returned in a list, e.g.:

// not possible
const result = await prisma
  .users()
  .links()

In this example, users() already returns a list, so it's not possible to query the links relation of each user object inside the list.

</Warning>

Examples

Query all the links of a single user:

const linksByUser = await prisma
  .user({ email: "[email protected]" })
  .links()

graphql

query {
  user(where: {
    email: "[email protected]"
  }) {
    links {
      id
      createdAt
      description
      url
    }
  }
}

</Code>

Query all the votes made by a certain user:

const votesByUser = await prisma
 .user({ email: "[email protected]" })
 .votes()

graphql

query {
 user(where: {
   email: "[email protected]"
 }) {
   votes {
     id
   }
 }
}

</Code>

Using fragments for fine-grained data access

Instead of querying all scalar fields of a model (which is the default behavior), you can specify which fields you'd like retrieve by using the $fragment API feature (based on GraphQL). This is useful to exclude large unneeded fields (like BLOB values or huge strings) or to even retrieve relations.

Examples

Fetch the name and email of the users as well the the description and url of their related links:

const fragment = `
fragment UserWithLinks on User {
  name
  email
  links {
    description
    url
  }
}
`

const userWithPosts = await prisma.users().$fragment(fragment)

graphql

query {
  users {
    ...UserWithLinks
  }
}

fragment UserWithLinks on User {
  name
  email
  links {
    description
    url
  }
}

</Code>

Basic filters for lists

Basic filters let you specify certain criteria to constrain which objects should be returned in a list. The filters are specified in the where object of the input argument which is accepted by any list query.

The type of the where object depends on the model for which it was generated.

View the type of where for Link here
View the type of where for User here
View the type of where for Vote here

</Collapse>

It is also possible to combine multiple filters using the AND and OR fields.

Examples

Fetch users that have an A in their names:

const usersWithAInName = await prisma
  .users({
    where: {
      name_contains: "A"
    }
  })

graphql

query {
  users(where: {
      name_contains: "A"
  }) {
    id
    name
    email
    password
  }
}

</Code> <Collapse title="Use auto-completion to explore the filter system">

</Collapse>

Fetch users called Alice or Bob:

const usersCalledAliceOrBob = await prisma
  .users({
    where: {
      name_in: ["Alice", "Bob"]
    }
  })

graphql

query {
  users(where: {
    name_in: ["Alice", "Bob"]
  }) {
    id
    name
    email
    password
  }
}

</Code>

Fetch links created before December 24, 2018:

const linksBeforeChristmas = await prisma
  .links({
    where: {
      createdAt_lt: "2018-12-24" 
    }
  })

graphql

query {
  links(where: {
    createdAt_lt: "2018-12-24" 
  }) {
    id
    createdAt
    description
    url
  }
}

</Code>

Dates and times in the Prisma client API follow the ISO 8601 standard which generally is of the form: YYYY-MM-DDThh:mm:ss. Learn more.

Fetch links that have prisma or graphql in their description and were created in 2018:

const filteredLinks = await prisma
  .links({
    where: {
      AND: [
        {
          OR: [{
            description_contains: "graphql",
          }, {
            description_contains: "prisma",
          }]
        }, 
        {
          AND: [{
            createdAt_gt: "2017"
          }, {
            createdAt_lt: "2019"
          }]
        }
      ],
    }
  })

graphql

query {
  links(where: {
    OR: [{
      description_contains: "graphql",
    }, {
      description_contains: "prisma",
    }]
    AND: [{ 
      createdAt_lt: "2019"
    }, { 
      createdAt_gt: "2017" 
    }]
  }) {
    id
    description
  }
}

</Code> <Info>

The AND filter can actually be omitted since multiple filter criteria are by default combined using a logical and. This means the above filter can also be expressed as follows:

const filteredLinks = await prisma
  .links({
    where: {
      OR: [{
        description_contains: "graphql"
      }, {
        description_contains: "prisma"
      }],
      createdAt_gt: "2017",
      createdAt_lt: "2019"
    }
  })

graphql

query {
  links(where: {
    OR: [{
      description_contains: "graphql",
    }, {
      description_contains: "prisma",
    }],
    createdAt_lt: "2019",
    createdAt_gt: "2017" 
  }) {
    id
    createdAt
    description
    url
  }
}

</Code> </Info>

Relational filters for lists

Relational filters can be used to constrain the returned objects on a relation list field. The types used for filtering are identical to basic filters, the only difference is that the filters are not applied on the first level of the method call but when querying a relation on the second level.

Examples

const linksByUserBeforeChristmas = await prisma
  .user({ email: "[email protected]" })
  .links({
    where: {
      createdAt_lt: "2017-12-24" 
    }
  })

graphql

query {
 user(where: {
  email: "[email protected]"
 }) {
    links(where: {
      createdAt_lt: "2017-12-24" 
    }) {
      id
      createdAt
      description
      url
  }
 }
}

</Code>

Ordering

When querying a list of model objects, you can order (sort) the list by any scalar field of that model type. Each generated method to query a list of models therefore accepts the orderBy field on its input object.

The type of the orderBy field depends on the scalar fields of the model for which it was generated.

View the type of orderBy for Link here
View the type of orderBy for User here
View the type of orderBy for Vote here

</Collapse>

Examples

Sort links by their creation date (ascending):

const sortedLinks = prisma
  .links({
    orderBy: "createdAt_ASC"
  })

graphql

query {
  links(orderBy: createdAt_ASC) {
    id
    createdAt
    description
    url
  }
}

</Code>

Sort users alphabetically by their names (descending):

const sortedUsers = prisma
  .users({
    orderBy: "name_DESC"
  })

graphql

query {
  users(orderBy: name_DESC) {
    id
    name
    email
    password
  }
}

</Code>

Pagination

When querying a list of model objects, you can fetch chunks of that list by supplying pagination arguments.

Seeking forward and backward with `first` and `last`

You can seek forwards or backwards through the objects and supply an optional starting object:

To seek forward, use first; specify a starting object with after.
To seek backward, use last; specify a starting object with before.

You cannot combine first with before or last with after. If you do so in a query, before/after will simply be ignored and only first or last is actually applied (at the very beginning or end of the list, depending on which you're using).

Note that you can query for more objects than actually exist in the database without an error message.

Skipping elements with `skip`

You can also skip an arbitrary amount of objects in whichever direction you are seeking by supplying the skip argument:

When using first, skip skips objects at the beginning of the list.
When using last, skip skips objects from the end of the list.

Examples

For the following examples, we're assuming a list of exactly 30 objects:

Query the first 3 links (seeking forward):

const links = await prisma
  .links({
    first: 3
  })

graphql

query {
  links(first: 3) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the objects from position 6 to position 10 (seeking forward):

const links = await prisma
  .links({
    first: 5, 
    skip: 5
  })

graphql

query {
  links(
    first: 5 
    skip: 5
  ) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the last 3 objects (seeking backward):

const links = await prisma
  .links({
    last: 3
  })

graphql

query {
  links(last: 3) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the objects from position 21 to position 27 (seeking backward):

const links = await prisma
  .links({
    last: 7,
    skip: 3
  })

graphql

query {
  links(
    last: 7
    skip: 3
  ) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the first 3 objects after the object with cixnen24p33lo0143bexvr52n as id:

const links = await prisma
  .links({
    first: 3,
    after: "cixnen24p33lo0143bexvr52n"
  })

graphql

query {
  links(
    first: 3
    after: "cixnen24p33lo0143bexvr52n"
  ) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the first 5 objects after the object with cixnen24p33lo0143bexvr52n as id and skipping 3 objects:

const links = await prisma
  .links({
    first: 5,
    after: "cixnen24p33lo0143bexvr52n",
    skip: 3
  })

graphql

query {
  links(
    first: 5
    after: "cixnen24p33lo0143bexvr52n"
    skip: 3
  ) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the last 5 objects before the object with cixnen24p33lo0143bexvr52n as id:

const links = await prisma
  .links({
    last: 5,
    before: "cixnen24p33lo0143bexvr52n"
  })

graphql

query {
  links(
    last: 5
    before: "cixnen24p33lo0143bexvr52n"
  ) {
    id
    createdAt
    description
    url
  }
}

</Code>

Query the last 3 nodes before the node with cixnen24p33lo0143bexvr52n as id and skipping 5 nodes:

const links = await prisma
  .links({
    last: 3,
    before: "cixnen24p33lo0143bexvr52n",
    skip: 5
  })

graphql

query {
  links(
    last: 3 
    before: "cixnen24p33lo0143bexvr52n"
    skip: 5
  ) {
    id
    createdAt
    description
    url
  }
}

</Code>

Aggregations

You can submit aggregation queries via connection queries. The following aggregation functions are supported:

count: Counts the number of objects in a list
avg (coming soon): Computes the average of a list of numbers.
median (coming soon): Computes the median of a list of numbers.
max (coming soon): Returns the greatest element of a list of numbers.
min (coming soon): Returns the smallest element of a list of numbers.
sum (coming soon): Computes the sum of a list of numbers.

See this GitHub issue to learn more about the upcoming aggregation functions.

Examples

Count the number of link objects:

const linkCount = await prisma
  .linksConnection()
  .aggregate()
  .count()

graphql

query {
  linksConnection {
    aggregate {
      count
    }
  }
}

</Code>

Overview

Fetching single objects

Examples

Fetching lists

Examples

Relations

Examples

Using fragments for fine-grained data access

Examples

Basic filters for lists

Examples

Relational filters for lists

Examples

Ordering

Examples

Pagination

Seeking forward and backward with first and last

Skipping elements with skip

Examples

Aggregations

Examples

Seeking forward and backward with `first` and `last`

Skipping elements with `skip`