哪位大哥能帮忙把下面2个简单的sqlserver下的函数转成oracle下面的函数

在插入新数据的时候，取出该字符串对应的字母

用户定义函数A
create function f_ch2py(@chn nchar(1))
returns char(1)
as
begin
declare @n int
declare @c char(1)
set @n = 63

select @n = @n +1,
@c = case chn when @chn then char(@n) else @c end
from(
select top 27 * from (
select chn =
'吖' union all select
'八' union all select
'嚓' union all select
'咑' union all select
'妸' union all select
'发' union all select
'旮' union all select
'铪' union all select
'丌' union all select --because have no 'i'
'丌' union all select
'咔' union all select
'垃' union all select
'嘸' union all select
'拏' union all select
'噢' union all select
'妑' union all select
'七' union all select
'呥' union all select
'仨' union all select
'他' union all select
'屲' union all select --no 'u'
'屲' union all select --no 'v'
'屲' union all select
'夕' union all select
'丫' union all select
'帀' union all select @chn) as a
order by chn COLLATE Chinese_PRC_CI_AS
) as b
return(@c)
end



用户定义函数B

CREATE FUNCTION F_GetHelpCode (
@cName VARCHAR(50) )
RETURNS VARCHAR(20)
AS
BEGIN
DECLARE @i SMALLINT, @L SMALLINT , @cHelpCode VARCHAR(20), @e VARCHAR(20), @iAscii SMALLINT
SELECT @i=1, @L=0 , @cHelpCode=''
while @L<=20 AND @i<=LEN(@cName) BEGIN
SELECT @e=LOWER(SUBSTRING(@cname,@i,1))
SELECT @iAscii=ASCII(@e)
IF @iAscii>=48 AND @iAscii <=57 OR @iAscii>=97 AND @iAscii <=122 or @iAscii=95
SELECT @cHelpCode=@cHelpCode +@e
ELSE
IF @iAscii>=176 AND @iAscii <=247
SELECT @cHelpCode=@cHelpCode + dbo.f_ch2py(@e)
ELSE SELECT @L=@L-1
SELECT @i=@i+1, @L=@L+1 END
RETURN @cHelpCode
END




调用方法
CREATE TRIGGER aa ON dbo.表A
FOR INSERT, UPDATE, DELETE
AS
update 表A set pinyin=dbo.F_GetHelpCode(b.item_name)
from 表A a,inserted b
where a.item_code=b.item_code