Baseline your database

JavaScript

MySQL

Create an initial migration

To use Prisma Migrate with the database you introspected in the last section, you will need to baseline your database.

Baselining refers to initializing your migration history for a database that might already contain data and cannot be reset, such as your production database. Baselining tells Prisma Migrate to assume that one or more migrations have already been applied to your database.

To baseline your database, use prisma migrate diff to compare your schema and database, and save the output into a SQL file.

First, create a migrations directory and add a directory inside with your preferred name for the migration. In this example, we will use 0_init as the migration name:

mkdir -p prisma/migrations/0_init

info

-p will recursively create any missing folders in the path you provide.

Next, generate the migration file with prisma migrate diff. Use the following arguments:

• --from-empty: assumes the data model you're migrating from is empty
• --to-schema-datamodel: the current database state using the URL in the datasource block
• --script: output a SQL script

npx prisma migrate diff --from-empty --to-schema-datamodel prisma/schema.prisma --script > prisma/migrations/0_init/migration.sql

Review the migration

The command will generate a migration that should resemble the following script:

prisma/migrations/0_init/migration.sql

-- CreateTable
CREATE TABLE `Post` (
    `id` INTEGER NOT NULL AUTO_INCREMENT,
    `title` VARCHAR(255) NOT NULL,
    `createdAt` TIMESTAMP(0) NOT NULL DEFAULT CURRENT_TIMESTAMP(0),
    `content` TEXT NULL,
    `published` BOOLEAN NOT NULL DEFAULT false,
    `authorId` INTEGER NOT NULL,

    INDEX `authorId`(`authorId`),
    PRIMARY KEY (`id`)
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- CreateTable
CREATE TABLE `Profile` (
    `id` INTEGER NOT NULL AUTO_INCREMENT,
    `bio` TEXT NULL,
    `userId` INTEGER NOT NULL,

    UNIQUE INDEX `userId`(`userId`),
    PRIMARY KEY (`id`)
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- CreateTable
CREATE TABLE `User` (
    `id` INTEGER NOT NULL AUTO_INCREMENT,
    `name` VARCHAR(255) NULL,
    `email` VARCHAR(255) NOT NULL,

    UNIQUE INDEX `email`(`email`),
    PRIMARY KEY (`id`)
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- AddForeignKey
ALTER TABLE `Post` ADD CONSTRAINT `Post_ibfk_1` FOREIGN KEY (`authorId`) REFERENCES `User`(`id`) ON DELETE RESTRICT ON UPDATE RESTRICT;

-- AddForeignKey
ALTER TABLE `Profile` ADD CONSTRAINT `Profile_ibfk_1` FOREIGN KEY (`userId`) REFERENCES `User`(`id`) ON DELETE RESTRICT ON UPDATE RESTRICT;

Review the SQL migration file to ensure everything is correct.

Next, mark the migration as applied using prisma migrate resolve with the --applied argument.

npx prisma migrate resolve --applied 0_init

The command will mark 0_init as applied by adding it to the _prisma_migrations table.

You now have a baseline for your current database schema. To make further changes to your database schema, you can update your Prisma schema and use prisma migrate dev to apply the changes to your database.