I have this model:

model Clan {
  id          Int    @id @default(autoincrement())
  owner       String @unique
  name        String
  level       Int    @default(1)
  description String @default("[ Описание клана отсутствует! ]")
  picture     String @default("<https://i.imgur.com/OLSFcu5.gif>")
  stars       Int    @default(0)
  voiceTime   Int    @default(0)

  monthActivityId  Int? @unique
  weeklyActivityId Int? @unique

  monthActivity  MonthActivity? @relation(fields: [monthActivityId], references: [id], onDelete: SetNull)
  weeklyActivity WeeklyActivity? @relation(fields: [weeklyActivityId], references: [id], onDelete: SetNull)

  user User[]
}

Activity models looks like:

model MonthActivity {
  id        Int @id @default(autoincrement())
  messages  Int @default(0)
  voiceTime Int @default(0)

  isClanActivity Boolean @default(false)

  clan Clan?
  user User?
}

as you can see, i setting null some fields if record about activity was deleted. And now i want to make same for clan. I mean, if i delete clan, i want to delete automatically activity records which binding for that clan by id. How i can implement this by prisma schema, or i should handle it on my own?