Prisma + Kysely: updatedAt NULL Constraint Error

The Problem

DatabaseError: null value in column "updatedAt" of relation "User" violates not-null constraint

When using Kysely for database operations with a Prisma-defined schema, inserting new records fails because the updatedAt column receives a null value, violating the NOT NULL constraint.

Root Cause

Prisma and Kysely operate at different levels:

• Prisma Schema: Defines the structure with special directives like @updatedAt
• Database Schema: The actual PostgreSQL table constraints
• Kysely: A query builder that interacts directly with the database, not through Prisma

When you use @updatedAt in Prisma, it only works when using Prisma Client. Kyrsey has no knowledge of this directive and assumes all Generated<Timestamp> columns will be handled by the database.

The disconnect: Your Prisma schema says updatedAt should have a default, but your actual PostgreSQL table might not have the DEFAULT CURRENT_TIMESTAMP constraint.

Why It Happens

Your migration files were created before the @updatedAt directive was added to the Prisma schema, or the migration didn't properly include the DEFAULT CURRENT_TIMESTAMP clause in the SQL.

Result: The column is NOT NULL but has no default value → database rejects NULL inserts.

Solutions

⭐ Best Solution: Helper Function (Recommended)

Create a utility function to consistently set timestamps in all Kysely inserts:

// utils/db-helpers.ts
export const getTimestamps = () => ({
  createdAt: new Date(),
  updatedAt: new Date(),
});

export const getUserInsertData = (data: Partial<User>) => ({
  ...data,
  ...getTimestamps(),
});

Then use it in your auth route:

// src/routes/auth.ts
const newUser = await db
  .insertInto('User')
  .values(getUserInsertData({
    email: registerData.email,
    password: hashedPassword,
    // ... other fields
  }))
  .executeTakeFirst();

Why this is best: - ✅ Works with future migrations (no conflicts) - ✅ DRY principle - reusable across all inserts - ✅ Consistent timestamp handling - ✅ No manual SQL or Prisma migrations needed - ✅ Explicit and maintainable

---

Why Other Solutions Don't Work

Database Defaults: Will be overwritten when new Prisma migrations are applied

-- ❌ This gets overwritten by next migration
ALTER TABLE "User" 
ALTER COLUMN "updatedAt" SET DEFAULT CURRENT_TIMESTAMP;

Prisma Migrations: @updatedAt only works with Prisma Client, not Kysely

updatedAt  DateTime   @updatedAt  // ❌ Kysely ignores this

Database Level Solution (not recommended)

Add a Postgres trigger that auto-updates updatedAt on row update. That's a DB-level guarantee independent of which client writes. But it's outside Prisma's schema — you'd manage it as a raw SQL migration. Up to you whether that's worth it; the helper approach is simpler.

Prevention Tips

1. Use Helper Functions for Timestamps
2. Create utility functions for all timestamp-related operations

3. Never manually set timestamps in individual queries

   export const getTimestamps = () => ({
     createdAt: new Date(),
     updatedAt: new Date(),
   });
   

4. When Mixing ORMs (Prisma + Kysely)

5. Recognize that Prisma directives (@updatedAt) don't apply to Kysely queries
6. Handle all required fields explicitly in code, not the database

7. Keep helper functions as the single source of truth

8. Avoid Database-Level Solutions

9. Don't add constraints directly via SQL—they get overwritten by migrations

10. Don't rely on Prisma directives for Kysely operations

11. Consistent Pattern for All Inserts

12. Apply timestamp helpers to all insert operations
13. Update, delete operations may also need similar helpers

Relevant Code Locations

• Prisma Schema: prisma/schema.prisma
• Migrations: prisma/migrations/
• Kysely Types: Generated types file (e.g., db/types.ts)
• Error Location: src/routes/auth.ts (line 69 in this case)

Checklist for Similar Issues

• [ ] Check if using multiple query builders (Prisma + Kysely, etc.)
• [ ] Verify migrations are applied: prisma migrate status
• [ ] Inspect migration SQL files for proper constraints
• [ ] Check Kysely type definitions for Generated<> markers
• [ ] Add DEFAULT CURRENT_TIMESTAMP or manually set values in inserts