/// <summary>
 /// 分组聚合条件(带判断)
 /// </summary>
 /// <typeparam name="THaving"></typeparam>
 /// <param name="where"></param>
 /// <param name="trueHavingExp"></param>
 /// <param name="falseHavingExp"></param>
 /// <returns></returns>
 public QuerySet <T> HavingIf <THaving>(bool where, Expression <Func <THaving, object> > trueHavingExp, Expression <Func <THaving, object> > falseHavingExp)
 {
     if (where)
     {
         HavingExpressionList.Add(trueHavingExp);
     }
     else
     {
         HavingExpressionList.Add(falseHavingExp);
     }
     return(this);
 }
 /// <summary>
 /// 分组聚合条件(根据指定表)
 /// </summary>
 /// <typeparam name="THaving"></typeparam>
 /// <param name="havingExp"></param>
 /// <returns></returns>
 public QuerySet <T> Having <THaving>(Expression <Func <THaving, object> > havingExp)
 {
     HavingExpressionList.Add(havingExp);
     return(this);
 }