How Can I map a database bool to a Rust bool variable?

[xiayulu]

Hello. I want to check if a record exists in my PostgreSQL database.
So I write a function like this:

    pub async fn nickname_exist(db: &PgPool, nickname: &String) -> Result<bool> {
        let is_exist =
            sqlx::query(r#"SELECT exists (SELECT 1 FROM users WHERE nickname = $1 LIMIT 1)"#)
                .bind(nickname)
                .map(|r: PgRow| r.get(0))  // I was confused here.
                .fetch_one(db)
                .await?;
        println!("{:?}", is_exist);
        Ok(true)
    }

I was confused by .map(|r: PgRow| r.get(0)) because there is no column name here.

[xiayulu]

Fine. I solved this problem by test in pgadmin:

So the column name is exists.

Hope This may Some one else.