How to fix P2025: An operation failed because it depends on one or more records that were required but not found in Prisma

// Check existence first
const user = await prisma.user.findUnique({
  where: { id: userId }
});

if (!user) {
  console.log('User not found');
  return null; // or throw a custom error
}

// Safe to proceed with operation
const deleted = await prisma.user.delete({
  where: { id: userId }
});

import { Prisma } from '@prisma/client';

async function updateUser(userId: string, data: any) {
  try {
    const user = await prisma.user.update({
      where: { id: userId },
      data
    });
    return user;
  } catch (error) {
    if (error instanceof Prisma.PrismaClientKnownRequestError) {
      if (error.code === 'P2025') {
        // Record not found - handle gracefully
        console.log('Cannot update: user not found');
        return null;
      }
    }
    // Re-throw other errors
    throw error;
  }
}

// updateMany returns a count, not the updated record
const result = await prisma.user.updateMany({
  where: { id: userId },
  data: { lastLogin: new Date() }
});

if (result.count === 0) {
  console.log('No users were updated - user not found');
} else {
  console.log(`Updated ${result.count} user(s)`);
}

// Bad: connect to a user that might not exist
const post = await prisma.post.create({
  data: {
    title: 'My Post',
    content: 'Content',
    author: {
      connect: { id: userId } // P2025 if user doesn't exist
    }
  }
});

// Good: verify the user exists first
const userExists = await prisma.user.findUnique({
  where: { id: userId },
  select: { id: true } // minimal select for performance
});

if (!userExists) {
  throw new Error('Cannot create post: author not found');
}

const post = await prisma.post.create({
  data: {
    title: 'My Post',
    content: 'Content',
    author: { connect: { id: userId } }
  }
});

// Old pattern (deprecated in v4, removed in v5)
const user = await prisma.user.findFirst({
  where: { email: '[email protected]' },
  rejectOnNotFound: true
});

// New pattern with findFirstOrThrow
try {
  const user = await prisma.user.findFirstOrThrow({
    where: { email: '[email protected]' }
  });
  // user is guaranteed to exist here
} catch (error) {
  if (error instanceof Prisma.PrismaClientKnownRequestError) {
    if (error.code === 'P2025') {
      // Handle not found case
      throw new UserNotFoundError();
    }
  }
  throw error;
}

// Instead of connect (which throws P2025 if category doesn't exist)
const post = await prisma.post.create({
  data: {
    title: 'My Post',
    category: { connect: { name: 'Technology' } }
  }
});

// Use connectOrCreate to handle both cases
const post = await prisma.post.create({
  data: {
    title: 'My Post',
    category: {
      connectOrCreate: {
        where: { name: 'Technology' },
        create: {
          name: 'Technology',
          description: 'Tech articles'
        }
      }
    }
  }
});