drizzle-best-practices

When to use

Use this skill when working with Drizzle ORM code. Agents often confuse Drizzle with Prisma and produce wrong schema syntax, incorrect relation patterns, or manual SQL where the query builder should be used.

Critical Rules

1. Schema definition: use pgTable/mysqlTable/sqliteTable, not Prisma-style

Wrong (agents do this):

model User {
  id    Int    @id @default(autoincrement())
  name  String
  posts Post[]
}

Correct:

import { pgTable, serial, text } from 'drizzle-orm/pg-core';

export const users = pgTable('users', {
  id: serial('id').primaryKey(),
  name: text('name').notNull(),
});

Why: Drizzle uses table-definition functions, not a Prisma-like DSL. Wrong syntax fails at compile time.

2. Relations: use relations(), not foreign key decorators

Wrong:

// Expecting Prisma-style @relation or Sequelize belongsTo

Correct:

import { relations } from 'drizzle-orm';

export const usersRelations = relations(users, ({ many }) => ({
  posts: many(posts),
}));

export const postsRelations = relations(posts, ({ one }) => ({
  author: one(users, { fields: [posts.authorId], references: [users.id] }),
}));

Why: Drizzle relations are defined separately from tables via relations(). Foreign keys go on the table; relation metadata goes in relations.

3. Queries: use query builder API, not raw SQL

Wrong:

const users = await db.execute(sql`SELECT * FROM users WHERE id = ${id}`);

Correct:

import { eq } from 'drizzle-orm';

const result = await db.select().from(users).where(eq(users.id, id));

Why: Query builder gives type safety, SQL injection protection, and dialect portability. Raw SQL only when the builder cannot express the query.

4. Type inference: use $inferSelect and $inferInsert

Wrong:

interface User {
  id: number;
  name: string;
}

Correct:

type SelectUser = typeof users.$inferSelect;
type InsertUser = typeof users.$inferInsert;

Why: Inferred types stay in sync with schema. Manual types drift and break on schema changes.

5. Prepared statements for frequent queries

Wrong:

for (const id of ids) {
  await db.select().from(users).where(eq(users.id, id));
}

Correct:

import { sql } from 'drizzle-orm';

const getById = db
  .select()
  .from(users)
  .where(eq(users.id, sql.placeholder('id')))
  .prepare();

for (const id of ids) {
  await getById.execute({ id });
}

Why: Prepared statements reduce parse/plan overhead and improve performance for repeated queries.

6. Transactions: use db.transaction()

Wrong:

await db.execute(sql`BEGIN`);
await db.insert(users).values(u);
await db.execute(sql`COMMIT`);

Correct:

await db.transaction(async (tx) => {
  await tx.insert(users).values(u);
  await tx.insert(posts).values(p);
});

Why: Drizzle transactions handle BEGIN/COMMIT/ROLLBACK and ensure the same connection is used throughout.

7. Migrations: drizzle-kit generate and migrate

Wrong:

// Hand-written 001_create_users.sql

Correct:

drizzle-kit generate
drizzle-kit migrate

Why: Generated migrations stay in sync with schema and support rollback. Manual SQL bypasses Drizzle's migration tracking.

8. Where clauses: use operators from drizzle-orm

Wrong:

db.select().from(users).where(sql`name = ${name}`);

Correct:

import { eq, like, gt, lt } from 'drizzle-orm';

db.select().from(users).where(eq(users.name, name));
db.select().from(users).where(like(users.name, '%foo%'));

Why: Operators are type-safe and parameterized. Raw template strings risk SQL injection.

9. Nested data: use relational queries

Wrong:

const users = await db.select().from(users);
for (const u of users) {
  u.posts = await db.select().from(posts).where(eq(posts.authorId, u.id));
}

Correct:

const usersWithPosts = await db.query.users.findMany({
  with: { posts: true },
});

Why: Relational API fetches nested data in one call with correct joins and typing.

10. Indexes: define in schema

Wrong:

// Separate migration: CREATE INDEX ...

Correct:

import { index } from 'drizzle-orm/pg-core';

export const users = pgTable('users', {
  id: serial('id').primaryKey(),
  email: text('email').notNull(),
}, (t) => [
  index('users_email_idx').on(t.email),
]);

Why: Indexes in schema are versioned and migrated with the rest of the schema.

11. Validation: use drizzle-zod

Wrong:

// Manually maintaining Zod schema that mirrors DB

Correct:

import { createInsertSchema } from 'drizzle-zod';

const insertUserSchema = createInsertSchema(usersTable);

Why: drizzle-zod derives Zod schemas from Drizzle tables, keeping validation in sync.

12. Connection pooling: configure for serverless

Wrong:

const db = drizzle(process.env.DATABASE_URL);

Correct:

import { drizzle } from 'drizzle-orm/postgres-js';
import postgres from 'postgres';

const client = postgres(url, { max: 10, idle_timeout: 20 });
const db = drizzle(client);

Why: Serverless needs bounded connections. Default pooling can exhaust DB connections.

Patterns

Export schema object for drizzle({ schema }) when using relational queries
Use .returning() after insert/update to get affected rows
Prefer findFirst over findMany when expecting a single row
Use .$dynamic() for conditional where/orderBy/limit

Anti-Patterns

Do not mix Prisma and Drizzle syntax
Do not use raw SQL for simple CRUD
Do not define manual types that duplicate schema
Do not use push in production; use generate + migrate
Do not create new db/drizzle instances per request in serverless