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

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.