02. Schema Definition and Data Modeling

7. Prisma Client Setup

In src/index.ts:

import { PrismaClient } from "@prisma/client";

const client = new PrismaClient();

async function main() {
  // write practice code here
}

main()
  .catch((error) => {
    console.error(error);
  })
  .finally(async () => {
    await client.$disconnect();
  });

Why $disconnect() matters:

• Prisma opens a database connection.
• At the end of your script, close it cleanly.

8. Create

Create one user:

const user = await client.user.create({
  data: {
    username: "utsav",
    password: "secret",
    age: 24,
    city: "lucknow",
  },
});

console.log(user);

Important:

• username is unique.
• Running this twice with the same username will fail.

9. Find Many

Get all users:

const users = await client.user.findMany();
console.log(users);

Get all todos:

const todos = await client.todo.findMany();
console.log(todos);

10. Find Unique

Use findUnique with unique fields like id or username.

const user = await client.user.findUnique({
  where: {
    username: "utsav",
  },
});

console.log(user);

Or:

const user = await client.user.findUnique({
  where: {
    id: 1,
  },
});

11. Find First

Use findFirst when the field is not unique.

const user = await client.user.findFirst({
  where: {
    city: "lucknow",
  },
});

console.log(user);

12. Filtering

Find users older than 18:

const users = await client.user.findMany({
  where: {
    age: {
      gt: 18,
    },
  },
});

Common filters:

gt      // greater than
gte     // greater than or equal
lt      // less than
lte     // less than or equal
contains
startsWith
endsWith
in
not

Example:

const users = await client.user.findMany({
  where: {
    city: {
      contains: "luck",
      mode: "insensitive",
    },
  },
});

13. Update

Update one user:

const updatedUser = await client.user.update({
  where: {
    username: "utsav",
  },
  data: {
    age: 25,
    city: "delhi",
  },
});

console.log(updatedUser);

Mark a todo as done:

const todo = await client.todo.update({
  where: {
    id: 1,
  },
  data: {
    done: true,
  },
});

14. Delete

Delete one todo:

await client.todo.delete({
  where: {
    id: 1,
  },
});

Delete many completed todos:

await client.todo.deleteMany({
  where: {
    done: true,
  },
});

Be careful with deleteMany. An empty where deletes all rows in that table.