I have an express server with Typescript Mysql also using Prisma Js for ORM. These are my schemas:

model Post {
  id          Int                 @id @default(autoincrement())
  title       String              @db.VarChar(35)
  description String              @db.VarChar(250)
  category    CategoriesOnPosts[]
  author      User                @relation(fields: [userId], references: [id])
  userId      String
  createdAt   DateTime            @default(now())
  updatedAt   DateTime            @updatedAt
}

model Category {
 id    Int                 @id @default(autoincrement())
 name  String              @unique @db.VarChar(18)
 about String              @db.VarChar(60)
 posts CategoriesOnPosts[]
}

model CategoriesOnPosts {
 post       Post     @relation(fields: [postId], references: [id])
postId     Int
category   Category @relation(fields: [categoryId], references: [id])
categoryId Int

 @@id([postId, categoryId])
}

first I create a new category then I will create a new post but I can't figure out this problem can any one help me ? also here is my requests:

export const createCategory = async (req: Request, res: Response) => {
 try {
   const { name, about } = req.body;
   if (!name || !about) return res.status(400).json({ error: 'Please fill all inputs!' });
   const existCategory = await prisma.category.findUnique({ where: { name } });
   if (existCategory) return res.status(400).json({ error: 'This category already exists!' });
   const category = await prisma.category.create({
     data: {
        name,
        about,
     },
  });
  res.status(201).json(category);
 } catch (error) {
  res.status(500).json({ error: error.message });
 }
};

but when I try to create a new post I can't see any category in CategoriesOnPosts model