Prisma explicit many to many field already defined - prisma

Question

I have comics which has many writers, artists and characters and i'm trying to join everything together in prisma, but struggling to understand what I'm doing wrong.
Comic schema:
model comics {
uniqueCoverId String #id
name String
artists comic_contributors[] #relation("artists")
writers comic_contributors[] #relation("writers")
}
Artists schema
model comic_artists {
id String #id #default(uuid())
name String?
comics comic_contributors[]
}
Writers schema
model comic_writers {
id String #id #default(uuid())
name String?
comics comic_contributors[]
}
Intermediary table
model comic_contributors {
writer_id String #unique
writer comic_writers? #relation("writers", fields: [writer_id], references: [id])
artist_id String #unique
artist comic_artists? #relation("artists", fields: [artist_id], references: [id])
##id([writer_id, artist_id])
}
When I try to format prisma it returns the errors
error: Field "comics" is already defined on model "comic_contributors".
comicsUniqueCoverId String?
comics comics? #relation(fields: [comicsUniqueCoverId], references: [uniqueCoverId])
error: Field "comicsUniqueCoverId" is already defined on model "comic_contributors".
comics comics? #relation(fields: [comicsUniqueCoverId], references: [uniqueCoverId])
comicsUniqueCoverId String?
Any suggestions on what I'm doing wrong please?

Answer 1

You don't need to explicit a many-to-many relationship table, Prisma is doing it for you!
Prisma implicit many-to-many
You only have to say:
model comics {
uniqueCoverId String #id
name String
artists comic_artists[]
writers comic_writers[]
}
model comic_artists {
id String #id #default(uuid())
name String?
comics comics[]
}
model comic_writers {
id String #id #default(uuid())
name String?
comics comics[]
}
and Prisma will create hidden relationship tables as
_comic_artitsTocomics
column A -> comic_artits.id
column B -> comics.uniqueCoverId
_comic_writersTocomics
column A -> comic_writers.id
column B -> comics.uniqueCoverId
This allow you to do
const comic = await prisma.comics.findUnique({
where: {
uniqueCoverId: 'UniqueCoverId',
},
include: {
artists: true,
writers: true,
},
});
And comic will looks like
{
uniqueCoverId: 'UniqueCoverId',
name: 'Name',
artists: [
{ id: '210059e6-00ab-448c-aea9-b706251ade52', name: 'Artist1' },
{ id: '38cd8efa-2a66-4fe5-ad47-ec4f511647c0', name: 'Artist2' },
{ id: '86d6c908-f17b-4fbd-b0ee-c314f06aeaa9', name: 'Artist3' }
],
writers: [
{ id: '9cf97bf4-9c43-4579-924b-15a7f5dcb3f9', name: 'Writer1' },
{ id: 'afe6eb2d-6d69-44f2-a491-14827dc94e66', name: 'Writer2' },
{ id: 'cdac61cf-339d-460d-960b-6581fa2d7a57', name: 'Writer3' }
]
}
Prisma explicit many-to-many
But if you really need an explicit many-to-many relationship to add some data on the relation it will looks like this schema
model comics {
uniqueCoverId String #id
name String
artists comic_artistsOncomics[]
writers comic_writersOncomics[]
}
model comic_artists {
id String #id #default(uuid())
name String?
comics comic_artistsOncomics[]
}
model comic_artistsOncomics {
uniqueCoverId String
comic comics #relation(fields: [uniqueCoverId], references: [uniqueCoverId])
artistId String
artist comic_artists #relation(fields: [artistId], references: [id])
// Some data
##id([uniqueCoverId, artistId])
}
model comic_writers {
id String #id #default(uuid())
name String?
comics comic_writersOncomics[]
}
model comic_writersOncomics {
uniqueCoverId String
comic comics #relation(fields: [uniqueCoverId], references: [uniqueCoverId])
writerId String
writer comic_writers #relation(fields: [writerId], references: [id])
// Some data
##id([uniqueCoverId, writerId])
}
The previous findUnique will now looks like
const test = await prisma.comics.findUnique({
where: {
uniqueCoverId: 'uniqueCoverId',
},
include: {
artists: {
include: {
artist: true,
},
},
writers: {
include: {
writer: true,
},
},
},
});
And the result
{
uniqueCoverId: "UniqueCoverId",
name: "Name",
artists: [
{
uniqueCoverId: "UniqueCoverId",
artistId: "210059e6-00ab-448c-aea9-b706251ade52",
artist: {
id: "210059e6-00ab-448c-aea9-b706251ade52",
name: "Artist1",
},
},
{
uniqueCoverId: "UniqueCoverId",
artistId: "38cd8efa-2a66-4fe5-ad47-ec4f511647c0",
artist: {
id: "38cd8efa-2a66-4fe5-ad47-ec4f511647c0",
name: "Artist2",
},
},
{
uniqueCoverId: "UniqueCoverId",
artistId: "86d6c908-f17b-4fbd-b0ee-c314f06aeaa9",
artist: {
id: "86d6c908-f17b-4fbd-b0ee-c314f06aeaa9",
name: "Artist3",
},
},
],
writers: [
{
uniqueCoverId: "UniqueCoverId",
writerId: "9cf97bf4-9c43-4579-924b-15a7f5dcb3f9",
writer: {
id: "9cf97bf4-9c43-4579-924b-15a7f5dcb3f9",
name: "Writer1",
},
},
{
uniqueCoverId: "UniqueCoverId",
writerId: "afe6eb2d-6d69-44f2-a491-14827dc94e66",
writer: {
id: "afe6eb2d-6d69-44f2-a491-14827dc94e66",
name: "Writer2",
},
},
{
uniqueCoverId: "UniqueCoverId",
writerId: "cdac61cf-339d-460d-960b-6581fa2d7a57",
writer: {
id: "cdac61cf-339d-460d-960b-6581fa2d7a57",
name: "Writer3",
},
},
],
}
EDIT FOR YOU TO TEST
model comics {
id String #id #default(uuid())
uniqueCoverId String #unique
name String
artists comic_artists[]
writers comic_writers[]
}
model comic_artists {
id String #id #default(uuid())
name String?
comics comics[]
}
model comic_writers {
id String #id #default(uuid())
name String?
comics comics[]
}