Databases & ORMs

npm install prisma @prisma/client
npx prisma init

DATABASE_URL="postgresql://user:password@localhost:5432/myapp"

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

generator client {
  provider = "prisma-client-js"
}

model User {
  id        String   @id @default(cuid())
  email     String   @unique
  name      String?
  posts     Post[]
  createdAt DateTime @default(now())
}

model Post {
  id        String   @id @default(cuid())
  title     String
  content   String?
  published Boolean  @default(false)
  author    User     @relation(fields: [authorId], references: [id])
  authorId  String
  createdAt DateTime @default(now())
}

import { prisma } from "@/lib/prisma"

// lib/prisma.ts — singleton pattern prevents multiple instances
import { PrismaClient } from "@prisma/client"
const globalForPrisma = globalThis as unknown as { prisma: PrismaClient }
export const prisma = globalForPrisma.prisma ?? new PrismaClient()
if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma

// app/posts/page.tsx — Server Component queries DB directly
export default async function PostsPage() {
  const posts = await prisma.post.findMany({
    where: { published: true },
    include: {
      author: {
        select: { name: true, email: true },
      },
    },
    orderBy: { createdAt: "desc" },
    take: 20,
  })

  return (
    <ul>
      {posts.map((post) => (
        <li key={post.id}>
          <h2>{post.title}</h2>
          <p>By {post.author.name}</p>
        </li>
      ))}
    </ul>
  )
}

# Create migration from schema changes
npx prisma migrate dev --name add-comment-model

# Apply to production
npx prisma migrate deploy

# Reset local DB
npx prisma migrate reset

import { PrismaClient } from "@prisma/client"

const prisma = new PrismaClient()

async function main() {
  const alice = await prisma.user.upsert({
    where: { email: "alice@example.com" },
    update: {},
    create: {
      email: "alice@example.com",
      name: "Alice",
      posts: {
        create: [
          { title: "Getting Started with Prisma", published: true },
          { title: "Advanced Queries", published: false },
        ],
      },
    },
  })
  console.log("Seeded:", alice)
}

main()
  .catch((e) => console.error(e))
  .finally(() => prisma.$disconnect())

# Add to package.json
# "prisma": { "seed": "tsx prisma/seed.ts" }
npx prisma db seed

// Include — fetch author with every post
const posts = await prisma.post.findMany({
  include: { author: true },
})

// Select — pick specific fields, deeply
const user = await prisma.user.findUnique({
  where: { email: "alice@example.com" },
  select: {
    name: true,
    posts: {
      where: { published: true },
      select: { title: true, createdAt: true },
      orderBy: { createdAt: "desc" },
    },
  },
})

// Nested create — user + post in one operation
const userWithPost = await prisma.user.create({
  data: {
    name: "Bob",
    email: "bob@example.com",
    posts: {
      create: { title: "First Post", content: "Hello world" },
    },
  },
  include: { posts: true },
})

// lib/prisma.ts — for serverless (Neon, PlanetScale)
import { PrismaClient } from "@prisma/client"
import { PrismaNeonHTTP } from "@prisma/adapter-neon"
import { Pool } from "@neondatabase/serverless"

const pool = new Pool({ connectionString: process.env.DATABASE_URL })
const adapter = new PrismaNeonHTTP(pool)
export const prisma = new PrismaClient({ adapter })