Prisma.js - How to insert into table that has many-to-many relationship

user_1817640 0
Viewed 881

How can I assign some tags to the post using Prisma.js?

I have some tags already and I want to assign some tags to the post? I don't want to create a new tag.

schema.prisma:

model Post {
  Id                 String           @id @default(uuid())
  AuthorId           String
  Author             User             @relation(fields: [AuthorId], references: [Id])
  CategoryId         String?
  Category           Category?        @relation(fields: [CategoryId], references: [Id])
  Title              String           @db.VarChar(255)
  Description        String?          @db.MediumText
  Summary            String?          @db.VarChar(255)

  Tags               TagPostMapping[]
}

model TagPostMapping {
  Id           String     @id @default(uuid())
  Post         Post?      @relation(fields: [PostId], references: [Id])
  PostId       String?
  Tag          Tag?       @relation(fields: [TagId], references: [Id])
  TagId        String?
  CreatedDate  DateTime   @default(now())
  ModifiedDate DateTime?  @updatedAt
}

model Tag {
  Id             String           @id @default(uuid())
  Title          String           @unique
  Posts          TagPostMapping[]
  CreatedDate    DateTime         @default(now())
  ModifiedDate   DateTime?        @updatedAt
}

In the Prisma website, there is an example but it's suitable for creating some tags and assign them to the Post. While I want to add some of the existing tags to the article.

https://www.prisma.io/docs/support/help-articles/working-with-many-to-many-relations#explicit-relations

prisma2 prisma node.js orm database
2 Answers

I had a similar situation and the below code worked for me:

  addTagToPost(addTagDto: AddTagDto): Promise<TagDto> {
    return prisma.tag.update({
      where: { Id: addTagDto.tagId },
      data: {
        Posts: {
          create: [
            {
              Post: {
                connect: {
                  Id: addTagDto.postId,
                },
              },
            },
          ],
        },
      },
    });
  }

PS: As Post and Tag have a many-to-many relationship, you can update prisma.post.update as well.

user_25008600

I have used $transaction and in this transaction I created 2 insert command also I have defined an Id for post with uuid package. postId = v4() . v4() is a function in uuid that generates a unique Id.

  public async Create(post: IPost): Promise<Post> {

    let postId = v4();
    let postTagIds: postTagMapping[] = [];
    post.Tags?.map(tag => postTagIds.push({ PostId: postId, TagId: tag.Id }));

    const transResult = await ApplicationDbContext.Prisma.$transaction([
      ApplicationDbContext.Prisma.post.create({
        data: {
          Id: postId,
          Title: post.Title,
          Summary: post.Summary,
          Description: post.Description,
          IsActive: post.IsActive,
          IsPublished: post.IsPublished,
          IsActiveNewComment: post.IsActiveNewComment,
          AuthorId: post.AuthorId,
          CategoryId: post.CategoryId,
        },
      }),
      ApplicationDbContext.Prisma.tagPostMapping.createMany({
        data: postTagIds
      })

    ]).finally(async () => {
      await ApplicationDbContext.Prisma.$disconnect();
    });

    let result = transResult as unknown as Post;

    return result;
  }
user_18176400
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