四舍六入五成双并保留一位有效位-数据修约

 C#

　　　　　/// <summary>
        /// 数据修约 -- 四舍六入5成双，至少保留一位有效位
        /// 数值0.00512，保留2位，修约为0.01
        /// </summary>
        /// <param name="modifyValue">原始数据</param>
        /// <param name="degit">保留位数</param>
        /// <returns></returns>
        public static string CalcValue(decimal modifyValue, int? degit)
        {
            decimal calValue = 0;
            int degitNotNull = degit ?? 2;

            calValue = Math.Round(modifyValue, degitNotNull);

            //按此修约为0则至少保留1位有效位数
            if (calValue == 0 && modifyValue != 0)
            {
                return modifyValue.ToString("G1");
            }
            else
            {
                return calValue.ToString("F" + degitNotNull);
            }
        }

　　　　　/// <summary>
        /// 数据修约 -- 四舍六入5成双，至少保留一位有效位
        /// 数值0.00512，保留2位，修约为0.005
        /// </summary>
        /// <param name="modifyValue">原始数据</param>
        /// <param name="degit">保留位数</param>
        /// <returns></returns>
        public static string CalcValue2(decimal modifyValue, int? degit)
        {
            decimal calValue = 0;
            int degitNotNull = degit ?? 2;

            if (Math.Abs(modifyValue) >= 1)
            {
                calValue = Math.Round(modifyValue, degitNotNull);
            }

            //按此修约为0则至少保留1位有效位数
            if (calValue == 0 && modifyValue != 0)
            {
                string value = modifyValue.ToString();
                //从小数点后
                value = value.Substring(value.IndexOf(".") + 1);
                for (int i = 0; i < value.Length; i++)
                {
                    if ((i + 1) < degitNotNull)
                    {
                        calValue = Math.Round(modifyValue, degitNotNull);
                    }
                    else
                    {
                        calValue = Math.Round(modifyValue, (i + 1));
                    }
                }
                return calValue.ToString();
            }
            else
            {
                return calValue.ToString("F" + degitNotNull);
            }
        }

        

SQL Server：

ROUND函数为四舍五入

/*四舍六入五成双*/
if object_id('fnRound') is not null 

  drop function fnRound 

  GO 

  create function fnRound(@num float,@i int) 

  returns varchar(20) 

  as 

  begin 

      declare @str varchar(20)     /*转换成字符类型*/ 

      declare @str2 varchar(20)    /*小数位数后面的字符串*/ 

      declare @str3 varchar(2)     /*小数位数字符串*/ 

      set @str = convert(varchar,@num) 

      if (charindex('.',reverse(@str)) <= 0) 

      begin 

      if @i > 0 

   begin 

   set @str = @str + '.' 

   while @i > 0 

    begin 

    set @str  = @str + '0' 

    set @i = @i - 1 

    end 

   end 

   return @str 

   end 

      set @str2 = reverse(substring(reverse(@str),1,charindex('.',reverse(@str)) - 1 - @i)) 

      set @str3 = substring(@str,charindex('.',@str) + 1,@i) 

      if @str2%5 = 0 and @str3%2 = 0   /*如果符合"五成双"*/ 

          set @str = substring(@str,1,charindex('.',@str) + @i) 

      else    /*否则四舍五入*/ 

          set @str = convert(varchar,round(@num,@i)) 

      RETURN @str 

  end 

  GO