/// <summary>
        /// 创建以delete from开头语的SQL语句
        /// </summary>
        /// <param name="tablename"></param>
        /// <param name="whereParam"></param>
        /// <returns></returns>
        public static DBBuilder Delete(string tablename = null, dynamic whereParam = null)
        {
            var builder = new DBBuilder("DELETE ");

            if (tablename != null)
            {
                builder.From(tablename);
            }
            if (whereParam != null)
            {
                builder.Where(whereParam);
            }
            return(builder);
        }
        /// <summary>
        /// 创建以select FieldName1,FieldName2 from TableName开头的SQL语句
        /// </summary>
        /// <param name="tablename">要查询的表名</param>
        /// <param name="whereParam">要查询的字段名</param>
        /// <returns></returns>
        public static DBBuilder Select(string tablename = null, object whereParam = null)
        {
            var builder = new DBBuilder("SELECT ");

            if (tablename != null)
            {
                builder.Append("*").From(tablename);
            }
            if (whereParam != null)
            {
                builder.Where(whereParam);
            }
            return(builder);
        }
        /// <summary>
        /// 创建以update开头语的SQL语句
        /// </summary>
        /// <param name="tablename"></param>
        /// <param name="setParam"></param>
        /// <param name="whereParam"></param>
        /// <returns></returns>
        public static DBBuilder Update(string tablename = null, dynamic setParam = null, dynamic whereParam = null)
        {
            var builder = new DBBuilder("UPDATE ");

            if (tablename != null)
            {
                builder.Table(tablename);
            }
            if (setParam != null)
            {
                builder.Set(setParam);
            }
            if (whereParam != null)
            {
                builder.Where(whereParam);
            }
            return(builder);
        }