sql sever 保留有效位数

GO
/****** Object:  UserDefinedFunction [dbo].[makedot]    Script Date: 2020/7/14 9:15:22 ******/
SET ANSI_NULLS ON;
GO
SET QUOTED_IDENTIFIER ON;
GO
-- =============================================
-- Author: Wjf
-- Create date: 2020/7/13
-- Description: <Description, ,>
-- =============================================
ALTER FUNCTION [dbo].[makedot]
(
    @var AS VARCHAR(50),
    @len AS INT
)
RETURNS VARCHAR(50)
AS
BEGIN

    DECLARE @ResultVar AS VARCHAR(50);
    DECLARE @DitIndex AS INT;

    SELECT @ResultVar = @var; --cast(@var as varchar(50));

    SELECT @DitIndex = CHARINDEX('.', @ResultVar);

    --补位变量
    DECLARE @Endvar AS NVARCHAR(50);
    DECLARE @i INT;

    --输入为小数时
    IF @DitIndex > 0
       AND @DitIndex < (@len + 1)
    BEGIN

        --位数小于有效位数
        IF LEN(@ResultVar) < (@len + 1)
        BEGIN
            SET @Endvar = N'';
            SET @i = 0;
            WHILE @i < ((@len + 1) - LEN(@ResultVar))
            BEGIN
                SET @Endvar = @Endvar + N'0';
                SET @i = @i + 1;
            END;
            SET @ResultVar = @ResultVar + @Endvar;
        END;
        ELSE
		--四舍五入
            --四舍五入
            SELECT @ResultVar = cast ( CAST(ROUND(@ResultVar, @len + 1 - @DitIndex)  AS  numeric(38,10) ) AS varchar(38));
			SELECT @ResultVar=SUBSTRING(@ResultVar,0, @len + 2)

    END;
    --输入为整数时
    ELSE
    BEGIN
        BEGIN
            --整数位小于有效位数
            IF LEN(@ResultVar) < @len
            BEGIN
                SET @Endvar = N'.';
                SET @i = 0;
                WHILE @i < (@len - LEN(@ResultVar))
                BEGIN
                    SET @Endvar = @Endvar + N'0';
                    SET @i = @i + 1;
                END;
                SET @ResultVar = @ResultVar + @Endvar;
            END;
			ELSE
			--四舍五入取整
			SELECT @ResultVar = ROUND(@ResultVar, 0);
        END;
    END;


    RETURN @ResultVar;
END;