typeorm findone subquery

TypeORM FindOne Subquery

TypeORM is an Object Relational Mapper (ORM) that allows you to interact with your database by using object-oriented programming. With TypeORM, you can write SQL queries in a more readable and maintainable way. One of the features of TypeORM is the "find one" method, which allows you to retrieve a single record from your database. In addition, you can use subqueries to filter your results and retrieve more specific data.

Using TypeORM FindOne Method

To use the "find one" method in TypeORM, you need to first create an instance of the repository class for the entity you want to query. Then, you can call the "findOne" method on the repository instance and pass in an optional set of criteria to filter your results. Here is an example:

// Import the necessary modules
import { getRepository } from "typeorm";
import { User } from "../entities";

// Get the repository instance
const userRepository = getRepository(User);

// Find a single user with the given ID
const user = await userRepository.findOne(1);

// Log the user object
console.log(user);

Using TypeORM Subqueries

In addition to filtering your results with the "findOne" method, you can also use subqueries to retrieve more specific data. A subquery is a query that is nested inside another query and is used to filter the results of the outer query.

Here is an example of using a subquery to find all users who have not made any purchases:

// Import the necessary modules
import { getRepository } from "typeorm";
import { User, Order } from "../entities";

// Get the repository instances
const userRepository = getRepository(User);
const orderRepository = getRepository(Order);

// Find all users who have not made any purchases
const users = await userRepository
    .createQueryBuilder("user")
    .where(`user.id NOT IN (${orderRepository.createQueryBuilder("order")
        .select("order.userId")
        .getSql()})`)
    .getMany();

// Log the user objects
console.log(users);