Where do I execute native SQL queries in Loopback 4? - sql

Question

I'm new to Loopback 4 and I've been trying to execute a native SQL query. I found how to do it, the thing is that don't have any clue of WHERE to put it in my code in order for it to work... here's the documentation I found.
I need to know where should I put this:
const result = await repository.execute('SELECT * FROM Products');
in my Loopback project, which has many files. My goal is to make a REST endpoint like /products/[name] with [name] being a parameter inserted dynamically to the SQL query.

Answer 1

You can do it in your controller class as per loopback docs https://loopback.io/doc/en/lb4/Controller.html. As you will define the REST endpoint in the controller itself you can also do the insertion there using repository.execute() e.g.
#get('/products/{name}')
async doSomething(
#param.path.string('name') name: string,
): Promise<Product> {
const sql = `SELECT * FROM some_table WHERE some_field="${name}"`;
await this.productRepository.execute(sql)
--- other lines of code & return value --
}

Answer 2

Personally, I would implement it as a new Repository method.
Let's say your model is called Product, then you should have src/repositories/product.repository.ts file exporting ProductRepository class already present in your project. (You can run lb4 repository to create it.)
export class Product extends DefaultCrudRepository<
Product,
typeof Product,
Product Relations
> {
constructor(#inject('datasources.db') dataSource: DbDataSource) {
super(Product, dataSource);
}
// your custom method
async selectByName(name: string): Promise<Product[]> {
const rawItems = await repository.execute('SELECT * FROM Products');
// would you like to convert raw data into Product instances?
return rawItems.map(it => new Product(it));
}
}
Then you can call this new custom repository method from your controller in the same way as you would call e.g. repository.find(filter).