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Add mutations allow you to add new objects of a particular type. We use the following schema to demonstrate some examples. Schema: 
type Author {
  id: ID!
  name: String! @search(by: [hash])
  dob: DateTime
  posts: [Post]
}

type Post {
  postID: ID!
  title: String! @search(by: [term, fulltext])
  text: String @search(by: [fulltext, term])
  datePublished: DateTime
}
Dgraph automatically generates input and return types in the schema for the add mutation, as shown below: 
addPost(input: [AddPostInput!]!): AddPostPayload

input AddPostInput {
  title: String!
  text: String
  datePublished: DateTime
}

type AddPostPayload {
  post(filter: PostFilter, order: PostOrder, first: Int, offset: Int): [Post]
  numUids: Int
}
Example: add mutation on single type with embedded value 
mutation {
  addAuthor(input: [{ name: "A.N. Author", posts: [] }]) {
    author {
      id
      name
    }
  }
}
Example: add mutation on single type using variables 
mutation addAuthor($author: [AddAuthorInput!]!) {
  addAuthor(input: $author) {
    author {
      id
      name
    }
  }
}
Variables: 
{ "author": { "name": "A.N. Author", "dob": "2000-01-01", "posts": [] } }
You can convert an add mutation to an upsert mutation by setting the value of the input variable upsert to true. For more information, see Upsert Mutations.

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Examples

You can refer to the following link for more examples.