Function quaint::ast::aggregate_to_string

pub fn aggregate_to_string<'a, T>(expr: T) -> AggregateToString<'a> where
    T: Into<DatabaseValue<'a>>, 

Aggregates the given field into a string.

let query = Select::from_table("users").value(aggregate_to_string(Column::new("firstName")))
    .group_by("firstName");

let (sql, _) = Sqlite::build(query);
assert_eq!("SELECT GROUP_CONCAT(`firstName`) FROM `users` GROUP BY `firstName`", sql);