Define a single-field primary key
A model needs one scalar primary key.
Prisma · Const
@id
@id defines a model's single-field identifier. In relational databases it represents a single-field primary key; compound identifiers use @@id.
How it works
Use @id on one scalar field to make that field the model's single-field identifier and primary key. The field may also use a default generator such as autoincrement(); for MongoDB, the field must additionally map to the underlying _id field.
Syntax
fieldName Type @idParameters
| Name | Type | Description |
|---|---|---|
field | scalar field | Optional field-level arguments and modifiers can be added to the annotated field, such as a default value generator; the referenced page's @id section does not define a standalone parameter list. |
Returns
Defines the model's single-field ID; it does not return a runtime value.
Key points
- @id marks one field as the model's single-field identifier.
- The ID distinguishes individual records within the model.
- Relational databases use @id for a single-field primary key.
- Use @@id instead when the identifier combines multiple fields.
Common mistakes
- A model cannot define multiple separate @id fields; use @@id when the identifier is compound.
- MongoDB requires the @id field to include @map("_id").
Example: Single-field model ID
model User {
id Int @id @default(autoincrement())
name String
}This model gives each User one integer primary key generated by the database.
When to use it
Combine with a default generator
Records need generated numeric identifiers.
Map MongoDB _id
A MongoDB model needs its required document identifier.
Interview questions
QWhat does @id do?
@id defines a single-field ID on a model. In relational databases, it represents the model's primary key, while a compound identifier uses @@id instead.
Follow-up: How would you model an identifier made from two fields? Use a model-level @@id([fieldA, fieldB]) declaration.
QHow many IDs can a Prisma model have?
A model may have only one ID. Put @id on the scalar field that uniquely identifies each record; use @unique for additional independently unique fields.
Follow-up: Can a model have both @id and @@id? No; the model has one ID, so choose either a single-field or compound definition.
QHow does @id differ across relational databases and MongoDB?
For MongoDB, the identifier must be a single field with @id and @map("_id"). Relational databases can use either a single-field @id or a multi-field @@id.
Follow-up: What is the relational alternative for a multi-field identifier? Declare @@id with the participating fields at model level.
Related
@@id@unique@@unique@default@map