Why do I need a DATABASE_URL env variable?

[HarrisonHemstreet]

I know that currently a database url is needed, but my question is, why do I need to make a DATABASE_URL environment variable when I already have made a pool like so? The decision to use a DATABASE_URL environment variable seems extremely redundant to me in this situation.

Or am I over looking something in my code? Do I not need a DATABASE_URL env variable in this situation?

PS: Bonus points if you can fix this code. 🙂

#[derive(Debug)]
struct Student {
    id: i32,
    name: String,
}

let pool = PgPoolOptions::new()
    .max_connections(5)
    .connect("postgres://root:root@localhost:5440/root")
    .await
    .unwrap();

let student = sqlx::query_as!(Student, "select * from student where id = 1")
    .fetch_one(&mut conn)
    .await?;

[VersBinarii]

The DATABASE_URL is needed for the sqlx to be able to connect to your database instance and validate that the SQL query i the query! macro is consistent with the actual database schema. This is done during compilation. Your pool is created during the runtime of your application.