How to update a many to many relationship in Prisma?

Question

I am modelling a boxing tournament.

Boxers and Fights have a many-to-many relationship:

• A Boxer has many Fights
• A Fight has many Boxers (exactly 2)

Here are the models in the schema

model Fight {
  id         Int     @id @default(autoincrement())
  name       String
  boxers     BoxerFights[]
}

model Boxer {
  id        Int     @id @default(autoincrement())
  name      String  @unique
  fights    BoxerFights[]
}

model BoxerFights {
  boxer      Boxer @relation(fields: [boxerId], references: [id])
  boxerId    Int
  fight      Fight @relation(fields: [fightId], references: [id])
  fightId    Int

  @@id([boxerId, fightId])
}

When creating a boxer I use the fight's name and the 2 boxer ids:

const fight = await prisma.fight.create({
  data: {
    name,
    boxers: {
      createMany: {
        data: [
          {
            boxerId: boxerId1,
          },
          {
            boxerId: boxerId2,
          },
        ],
      },
    },
  },
})

How would I update the fight if a boxer needed to be changed? Something like this? I'm not sure if I use update and set

const fight = await prisma.fight.update({
  data: {
    name: newName,
    boxers: {
      set: {
        data: [
          {
            boxerId: newBoxerId1,
          },
          {
            boxerId: newBoxerId2,
          },
        ],
      },
    },
  },
})

Answer 1

Here you go an example how to do that:

const { PrismaClient } = require('@prisma/client')
const prisma = new PrismaClient()

const saveData = async () => {
  const boxer1 = await prisma.boxer.create({
    data: {
      name: 'Boxer1',
    },
  })

  const boxer2 = await prisma.boxer.create({
    data: {
      name: 'Boxer2',
    },
  })
  const fight = await prisma.fight.create({
    data: {
      name: 'Fight 1',
      boxers: {
        createMany: {
          data: [
            { boxerId: boxer1.id },
            { boxerId: boxer2.id },
          ]
        },
      }
    },
    select: {
      id: true,
      name: true,
      boxers: {
        select: {
          boxer: {
            select: {
              name: true,
            }
          }
        }
      }
    }
  })

  console.log(JSON.stringify(fight, null, 2))

  const boxer3 = await prisma.boxer.create({
    data: {
      name: 'Boxer3',
    },
  })
  
  const fightUpdated = await prisma.fight.update({
    where: {
      id: fight.id
    },
    data: {
      boxers: {
        createMany: {
          data: [
            { boxerId: boxer3.id },
          ]
        },
        deleteMany: {
          OR: [
            { boxerId: { equals: boxer1.id } },
          ]
        }
      }
    },
    select: {
      name: true,
      boxers: {
        select: {
          boxer: {
            select: {
              name: true,
            }
          }
        }
      }
    }
  })

  console.log(JSON.stringify(fightUpdated, null, 2))

}

saveData()

In the update you have to remove the previous boxer and the new one :)