The sqlx documentation states:

Enumerations may be defined in Rust and can match SQL by integer discriminant or variant name.

With #[repr(_)] the integer representation is used when converting from/to SQL and expects that SQL type (e.g., INT). Without, the names of the variants are used instead and expects a textual SQL type (e.g., VARCHAR, TEXT).

source: Type in sqlx - Rust

When I implement this in the example below a runtime error is thrown:

thread 'omp_db::test_sqlx_types::test_sqlx_locale' (84932) 
panicked at src/omp_db.rs:403:62:
fetched locale: ColumnDecode { 
  index: "0",
  source: "mismatched types; 
  Rust type `oai_to_alma::omp_db::test_sqlx_types::Locale` (as SQL type `ENUM`) 
  is not compatible with SQL type `VARCHAR`"
}

What is wrong here?

#[cfg(test)]
mod test_sqlx_types {
    use std::sync::LazyLock;

    use sqlx::{MySql, Pool, mysql::MySqlPoolOptions};

    use crate::config::Config;

    pub static DB: LazyLock<Pool<MySql>> = LazyLock::new(|| {
        async_std::task::block_on(async {
            let url = format!(
                "mysql://{}:{}@{}:{}/{}",
                // fill in your values when testing
                "db.user",
                "db.password",
                "db.host",
                "db.port",
                "db.database"
            );
            MySqlPoolOptions::new()
                .max_connections(5)
                .connect(&url)
                .await
                .expect("successfully connected to MySQL OMP  database")
        })
    });

    #[derive(Debug, sqlx::Type)]
    #[allow(non_camel_case_types)]
    pub enum Locale {
        de_DE,
        en_US,
    }

    #[test]
    fn test_sqlx_locale() {
        let query = sqlx::query_scalar(r#"select 'en_US'"#);
        let locale: Locale = async_std::task::block_on(query.fetch_one(&*DB))
            .expect("fetched locale");
        dbg!(locale);
    }
}

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