Migrate MongoDB to MySQL using Prism Key Differences

The schema.prisma file defines the data models, relationships, and database connection details for Prisma. When using different databases like MongoDB and MySQL, the schema.prisma file will have differences due to the unique characteristics and data types of each database.

Key Differences Between schema.prisma for MongoDB and MySQL

1. Datasource Configuration

The datasource block specifies the database provider (mongodb or mysql) and connection details. The provider will change depending on the database you are using.

• MongoDB Configuration:

  datasource db {
    provider = "mongodb"
    url      = env("DATABASE_URL")
  }

• MySQL Configuration:

  datasource db {
    provider = "mysql"
    url      = env("DATABASE_URL")
  }

2. Data Model Differences

MongoDB and MySQL have different data types and ways of defining primary keys and relationships. Here are the primary differences:

• Primary Key Definition:

  • In MongoDB, the primary key is usually an ObjectId and is mapped using the @map("_id") directive.
  • In MySQL, the primary key is typically an integer with auto-increment.

• Data Type Differences:

  • MongoDB supports data types like String, Int, Float, Boolean, DateTime, and custom types like Json and ObjectId.
  • MySQL has a more structured type system, including Int, Float, Double, Boolean, DateTime, Decimal, and String.

Example of schema.prisma for MongoDB:

datasource db {
  provider = "mongodb"
  url      = env("DATABASE_URL")
}

generator client {
  provider = "prisma-client-js"
}

model User {
  id    String @id @default(auto()) @map("_id") @db.ObjectId
  name  String
  email String @unique
  posts Post[]
}

model Post {
  id        String   @id @default(auto()) @map("_id") @db.ObjectId
  title     String
  content   String
  published Boolean  @default(false)
  authorId  String   @db.ObjectId
  author    User?    @relation(fields: [authorId], references: [id])
}

Example of schema.prisma for MySQL:

datasource db {
  provider = "mysql"
  url      = env("DATABASE_URL")
}

generator client {
  provider = "prisma-client-js"
}

model User {
  id    Int    @id @default(autoincrement()) // Integer auto-increment primary key
  name  String
  email String @unique
  posts Post[]
}

model Post {
  id        Int     @id @default(autoincrement())
  title     String
  content   String
  published Boolean  @default(false)
  authorId  Int
  author    User     @relation(fields: [authorId], references: [id])
}

Summary of Differences

Feature	MongoDB (schema.prisma)	MySQL (schema.prisma)
Datasource Provider	provider = "mongodb"	provider = "mysql"
Primary Key Definition	id String @id @default(auto()) @map("_id") @db.ObjectId	id Int @id @default(autoincrement())
Data Types	Supports String, Int, Float, Boolean, DateTime, etc.	More structured, includes Int, Float, Double, etc.
Foreign Key Relationship	Foreign keys defined with @db.ObjectId	Foreign keys with Int or other standard SQL types
Autoincrement ID	Not applicable (@default(auto()))	@default(autoincrement())
Unique Identifier	@unique for unique fields	@unique for unique fields

Conclusion

The main differences in the schema.prisma file between MongoDB and MySQL revolve around how primary keys are handled, the differences in data types, and the way relationships and fields are mapped to the database. When switching from MongoDB to MySQL, these differences must be adjusted to accommodate the underlying database system's constraints and data modeling.