/// <summary>
 /// 获取指定字段的聚合函数值
 /// </summary>
 /// <param name="fieldName">字段名</param>
 /// <param name="condition">查询条件(不包含WHERE)</param>
 /// <returns>总数</returns>
 public virtual int GetMin(string fieldName, string condition = null)
 {
     return(DbUtil.AggregateInt(DbHelper, CurrentTableName, fieldName, condition: condition, function: "MIN"));
 }