  def self.get_using_size(mail_account_id, add_con=nil)

    SqlHelper.validate_token([mail_account_id])

    con = []
    con << "(mail_account_id=#{mail_account_id})"
    con << "(#{add_con})" unless add_con.nil? or add_con.empty?

    return (Email.count_by_sql("select SUM(size) from emails where #{con.join(' and ')}") || 0)
  end
The software constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component.