How to check if result of request to DB is empty?

[Suliman via Digitalmars-d-learn]

I am using https://github.com/buggins/ddbc
string query_string = (`SELECT user, password FROM otest.myusers 
where user LIKE ` ~ `'%` ~ request["username"].to!string ~ `%';`);
        auto rs = db.stmt.executeQuery(query_string);

        string dbpassword;
        string dbuser;

        while (rs.next())
        {
            dbuser = rs.getString(1);
            dbpassword = rs.getString(2);
            writeln(dbuser);
            writeln("Place seems unreachable"); // if SQL result 
is empty
...

How I can check if SQL request returned empty result?