ずっと気がかりなことがありました。
そもそも四半期の計算にループ要るのかなぁって

dbo.fiscalyear

 CREATE FUNCTION dbo.fiscalyear(
					@Date Datetime2,
					@ClosingMonth int = 3)
returns @FiscalElements table
~~
--This part sets fiscalyear of @Date.
--この部分で会計年度をセット
if(@innermonth > @ClosingMonth)
set @inneryear  = year(@date);
else
set @inneryear = year(@date) - 1;
--This part sets quarterpart  of @Date.
--この部分で四半期をセット
declare @repeatmonth as int;
set @repeatmonth = 0;
declare  @relativemonth as int;
set @relativemonth =  dbo.MonthCorretion(@ClosingMonth +@repeatmonth + 1);
declare @quarterpart int;
while @repeatmonth < 13
	begin
	if (@relativemonth = @innermonth)
		begin 
			set @quarterpart = cast((@repeatmonth  / 3) as int)+1;
			break;
		end
	else
		begin
			set @repeatmonth = @repeatmonth + 1;
			set @relativemonth = dbo.MonthCorretion(@relativemonth + 1);
			continue;
		end
	end

これを少しリファクタリングします。ループなしで実装しなおすと

dbo.fiscalyear2

--This part sets fiscalyear and quarterpart from @Date.
--この部分で会計年度と四半期をセット
declare  @relativemonth as int;
declare  @quarterpart as int; 
if (@innermonth > @ClosingMonth)
    begin
        set @inneryear  = year(@date);
        set @relativemonth =(@innermonth -@ClosingMonth-1);
    end 
else
    begin
        set @inneryear = year(@date) - 1;
        set @relativemonth =(11 + @innermonth -@ClosingMonth);
    end
set @quarterpart = cast((@relativemonth  / 3) as int)+1;

これでループを排除できたことになる。
このループを排除したfiscalyearの全文を並べると

dbo.fiscalyear2

 CREATE FUNCTION dbo.fiscalyear(
					@Date Datetime2,
					@ClosingMonth int = 3)
returns @FiscalElements table
(
	date Datetime2 Not null,
	fiscalyear int Not null,
	quarterpart int Not null,
	quarterparthanji char(18) Not null
)
as
begin

declare @innermonth as int;
declare @inneryear as int;
set @innermonth = month(@Date);

--This part sets fiscalyear and quarterpart from @Date.
--この部分で会計年度と四半期をセット
declare  @relativemonth as int;
declare  @quarterpart as int; 
if (@innermonth > @ClosingMonth)
    begin
        set @inneryear  = year(@date);
        set @relativemonth =(@innermonth -@ClosingMonth-1);
    end 
else
    begin
        set @inneryear = year(@date) - 1;
        set @relativemonth =(@innermonth -@ClosingMonth -1 +12);
    end
set @quarterpart = cast((@relativemonth  / 3) as int)+1;

--this part sets japanese quaterpart in character.
--この部分では文字列四半期を設定する。
declare @qparthanzi char(2);

if (@quarterpart=1) set @qparthanzi = '壱'
if (@quarterpart=2) set @qparthanzi = '弐'
if (@quarterpart=3) set @qparthanzi = '参'
if (@quarterpart=4) set @qparthanzi = '肆'

insert  @FiscalElements(date,fiscalyear,quarterpart,quarterparthanji)
values (@Date,@inneryear,@quarterpart,cast(@inneryear as char(4)) + '年度第' + @qparthanzi + '四半期')
return 
end

以上