How to link many to many items in Prisma without duplicates - sql

Question

I have many to many relationships between Product and Menu.
model Product {
id Int #id #default(autoincrement())
name String
price Float
description String?
product_category ProductCategory #relation(fields: [category_id], references: [id])
category_id Int
menus MenuProducts[]
created_at DateTime #default(now())
updated_at DateTime #updatedAt
##map("products")
}
model Menu {
id Int #id #default(autoincrement())
name String
products MenuProducts[]
created_at DateTime #default(now())
updated_at DateTime #updatedAt
##map("menus")
}
model MenuProducts {
menu_id Int
menu Menu #relation(fields: [menu_id], references: [id])
product_id Int
product Product #relation(fields: [product_id], references: [id])
created_at DateTime #default(now())
updated_at DateTime #updatedAt
##map("menu_products")
##id([product_id, menu_id])
}
In the menu update, I want to assign many products to the menu.
I've tried like this:
this.prisma.menu.update({where: {id}, data: {...updateMenuDto, products: {connect: {id: 6}}}});
but I received this error:
The required connected records were not found. Expected 1 records to be connected after connect operation on one-to-many relation 'MenuToMenuProducts', found 0.
Anyway, I've tried like this:
this.prisma.menuProducts.create({data:{menu: {connect: {id: id}},product: {connect: {id: 6}}}})
and it worked, but on the second call I saw what the line was duplicated. How I can link multiple products to menu without inserting duplicates?

Answer 1

To remove duplicates from the MenuProducts model you can define a unique constraint on the combination of product_id and menu_id which will restrict having duplication of product and menu id.
model MenuProducts {
menu_id Int
menu Menu #relation(fields: [menu_id], references: [id])
product_id Int
product Product #relation(fields: [product_id], references: [id])
created_at DateTime #default(now())
updated_at DateTime #updatedAt
##map("menu_products")
##id([product_id, menu_id])
##unique([product_id, menu_id])
}
Here is a reference of ##unique constraint.