Macro diesel::no_arg_sql_function

macro_rules! no_arg_sql_function {
    ($type_name:ident, $return_type:ty) => { ... };
    ($type_name:ident, $return_type:ty, $docs:expr) => { ... };
    ($type_name:ident, $return_type:ty, $docs:expr, $($constraint:ident)::+) => { ... };
}

Declare a 0 argument SQL function for use in your code. This will generate a unit struct, which is an expression representing calling this function. See now for example output. now was generated using:

no_arg_sql_function!(now, sql_types::Timestamp, "Represents the SQL NOW() function");

You can optionally pass the name of a trait, as a constraint for backends which support the function.