Introspection

JavaScript

SQL Server

Introspect your database with Prisma ORM

For the purpose of this guide, we'll use a demo SQL schema with three tables:

CREATE TABLE [dbo].[Post] (
    [id] INT NOT NULL IDENTITY(1,1),
    [createdAt] DATETIME2 NOT NULL CONSTRAINT [Post_createdAt_df] DEFAULT CURRENT_TIMESTAMP,
    [updatedAt] DATETIME2 NOT NULL,
    [title] VARCHAR(255) NOT NULL,
    [content] NVARCHAR(1000),
    [published] BIT NOT NULL CONSTRAINT [Post_published_df] DEFAULT 0,
    [authorId] INT NOT NULL,
    CONSTRAINT [Post_pkey] PRIMARY KEY ([id])
);

CREATE TABLE [dbo].[Profile] (
    [id] INT NOT NULL IDENTITY(1,1),
    [bio] NVARCHAR(1000),
    [userId] INT NOT NULL,
    CONSTRAINT [Profile_pkey] PRIMARY KEY ([id]),
    CONSTRAINT [Profile_userId_key] UNIQUE ([userId])
);

CREATE TABLE [dbo].[User] (
    [id] INT NOT NULL IDENTITY(1,1),
    [email] NVARCHAR(1000) NOT NULL,
    [name] NVARCHAR(1000),
    CONSTRAINT [User_pkey] PRIMARY KEY ([id]),
    CONSTRAINT [User_email_key] UNIQUE ([email])
);

ALTER TABLE [dbo].[Post] ADD CONSTRAINT [Post_authorId_fkey] FOREIGN KEY ([authorId]) REFERENCES [dbo].[User]([id]) ON DELETE NO ACTION ON UPDATE CASCADE;

ALTER TABLE [dbo].[Profile] ADD CONSTRAINT [Profile_userId_fkey] FOREIGN KEY ([userId]) REFERENCES [dbo].[User]([id]) ON DELETE NO ACTION ON UPDATE CASCADE;

Expand for a graphical overview of the tables

User

Column name	Type	Primary key	Foreign key	Required	Default
id	INT	✔️	No	✔️	autoincrementing
name	NVARCHAR(1000)	No	No	No	-
email	NVARCHAR(1000)	No	No	✔️	-

Post

Column name	Type	Primary key	Foreign key	Required	Default
id	INT	✔️	No	✔️	autoincrementing
createdAt	DATETIME2	No	No	✔️	now()
updatedAt	DATETIME2	No	No	✔️
title	VARCHAR(255)	No	No	✔️	-
content	NVARCHAR(1000)	No	No	No	-
published	BIT	No	No	✔️	false
authorId	INT	No	✔️	✔️	-

Profile

Column name	Type	Primary key	Foreign key	Required	Default
id	INT	✔️	No	✔️	autoincrementing
bio	NVARCHAR(1000)	No	No	No	-
userId	INT	No	✔️	✔️	-

As a next step, you will introspect your database. The result of the introspection will be a data model inside your Prisma schema.

Run the following command to introspect your database:

npx prisma db pull

This command reads the DATABASE_URL environment variable that's defined in .env and connects to your database. Once the connection is established, it introspects the database (i.e. it reads the database schema). It then translates the database schema from SQL into a Prisma data model.

After the introspection is complete, your Prisma schema is updated:

The data model now looks similar to this (note that the fields on the models have been reordered for better readability):

prisma/schema.prisma

model Post {
  id        Int      @id @default(autoincrement())
  title     String   @db.VarChar(255)
  createdAt DateTime @default(now()) @db.Timestamp(6)
  content   String?
  published Boolean  @default(false)
  authorId  Int
  User      User     @relation(fields: [authorId], references: [id])
}

model Profile {
  id     Int     @id @default(autoincrement())
  bio    String?
  userId Int     @unique
  User   User    @relation(fields: [userId], references: [id])
}

model User {
  id      Int      @id @default(autoincrement())
  name    String?  @db.VarChar(255)
  email   String   @unique @db.VarChar(255)
  Post    Post[]
  Profile Profile?
}

Prisma's data model is a declarative representation of your database schema and serves as the foundation for the generated Prisma Client library. Your Prisma Client instance will expose queries that are tailored to these models.

Right now, there's a few minor "issues" with the data model:

• The User relation field is uppercased and therefore doesn't adhere to Prisma's naming conventions . To express more "semantics", it would also be nice if this field was called author to describe the relationship between User and Post better.
• The Post and Profile relation fields on User as well as the User relation field on Profile are all uppercased. To adhere to Prisma's naming conventions , both fields should be lowercased to post, profile and user.
• Even after lowercasing, the post field on User is still slightly misnamed. That's because it actually refers to a list of posts – a better name therefore would be the plural form: posts.

These changes are relevant for the generated Prisma Client API where using lowercased relation fields author, posts, profile and user will feel more natural and idiomatic to JavaScript/TypeScript developers. You can therefore configure your Prisma Client API.

Because relation fields are virtual (i.e. they do not directly manifest in the database), you can manually rename them in your Prisma schema without touching the database:

prisma/schema.prisma

model Post {
  id        Int      @id @default(autoincrement())
  title     String   @db.VarChar(255)
  createdAt DateTime @default(now()) @db.Timestamp(6)
  content   String?
  published Boolean  @default(false)
  author    User     @relation(fields: [authorId], references: [id])
  authorId  Int
}

model Profile {
  id     Int     @id @default(autoincrement())
  bio    String?
  user   User    @relation(fields: [userId], references: [id])
  userId Int     @unique
}

model User {
  id      Int      @id @default(autoincrement())
  email   String   @unique @db.VarChar(255)
  name    String?  @db.VarChar(255)
  posts   Post[]
  profile Profile?
}

In this example, the database schema did follow the naming conventions for Prisma ORM models (only the virtual relation fields that were generated from introspection did not adhere to them and needed adjustment). This optimizes the ergonomics of the generated Prisma Client API.

Using custom model and field names

Sometimes though, you may want to make additional changes to the names of the columns and tables that are exposed in the Prisma Client API. A common example is to translate snake_case notation which is often used in database schemas into PascalCase and camelCase notations which feel more natural for JavaScript/TypeScript developers.

Assume you obtained the following model from introspection that's based on snake_case notation:

model my_user {
  user_id    Int     @id @default(autoincrement())
  first_name String?
  last_name  String  @unique
}

If you generated a Prisma Client API for this model, it would pick up the snake_case notation in its API:

const user = await prisma.my_user.create({
  data: {
    first_name: 'Alice',
    last_name: 'Smith',
  },
})

If you don't want to use the table and column names from your database in your Prisma Client API, you can configure them with @map and @@map:

model MyUser {
  userId    Int     @id @default(autoincrement()) @map("user_id")
  firstName String? @map("first_name")
  lastName  String  @unique @map("last_name")

  @@map("my_user")
}

With this approach, you can name your model and its fields whatever you like and use the @map (for field names) and @@map (for models names) to point to the underlying tables and columns. Your Prisma Client API now looks as follows:

const user = await prisma.myUser.create({
  data: {
    firstName: 'Alice',
    lastName: 'Smith',
  },
})

Learn more about this on the Configuring your Prisma Client API page.