query查询多层次一对多关系， 再将首层SaleActivityBo和第二层SaleContentBo、EffectiveAreaBo查出来之后，第三层的SaleRuleBo是否必须for循环第二层的saleContentBoList然后才能查询出来第三层的值，有没有其他的方式，for数据库效率太低

  public void aa() {
        List<SaleActivityBo> saleActivityBoList = dao().query(SaleActivityBo.class, null);
        System.out.println(saleActivityBoList);
        saleActivityBoList = dao().fetchLinks(saleActivityBoList, null);
        System.out.println(saleActivityBoList);
        for (SaleActivityBo saleActivityBo : saleActivityBoList) {
            List<SaleContentBo> saleContentBoList = saleActivityBo.getSaleContentBoList();
            saleContentBoList = dao().fetchLinks(saleContentBoList, null);
        }
        System.out.println(saleActivityBoList);
    }

public class SaleActivityBo extends SaleActivity {
    private EnumSaleActivityStatusPhase saleActivityStatusPhase;

    /**
     * 生效区域的集合
     */
    @Many(field = "saleActivityId")
    private List<EffectiveAreaBo> effectiveAreaBoList;


    /**
     * 优惠内容的集合
     */
    @Many(field = "saleActivityId")
    private List<SaleContentBo> saleContentBoList;

}

public class SaleContentBo extends SaleContent {

    /**
     * 保存营销规则的集合
     */
    @Many(field = "saleContentId")
    private List<SaleRuleBo> saleRuleBoList;
}