[求助][em03]新手求指教，这个SQL语句该怎么写

我有数据如下：

建表脚本：
create table tb_test(ID int identity(1,1) primary key,AU nvarchar(300))
go
insert into tb_test(AU)
select 'Liu, C; Li, LC; Chen, WQ; Chen, X; Xu, ZH; Bai, SN'
union
select 'Ji, YS; Guo, HW'
union
select 'Cui, WY; Zhao, SF; Polanowska-Grabowska, R; Wang, J; Wei, JX; Dash, B; Chang, SL; Saucerman, JJ; Gu, J; Li, MD'
union
select 'Xiao, A; Wu, YD; Yang, ZP; Hu, YY; Wang, WY; Zhang, YT; Kong, L; Gao, G; Zhu, ZY; Lin, S; Zhang, B'
union
select 'Song, CX; Yi, CQ; He, C'
union
select 'Fan, XX; Zhou, YF; Liu, X; Li, LF; Su, XD'
union
select 'Wen, X; Zhang, CL; Ji, YS; Zhao, Q; He, WR; An, FY; Jiang, LW; Guo, HW'
union
select 'Wang, Q; Fristedt, R; Yu, XH; Chen, ZG; Liu, HT; Lee, Y; Guo, HW; Merchant, SS; Lin, CT'
union
select 'Liang, YH; Gao, R; Su, XD'
union
select 'Zhao, L; Ding, Q; Zeng, J; Wang, FR; Zhang, J; Fan, SJ; He, XQ'
go

从网上找了个函数可以按分号把AU（作者）字段按顺序拆成列：
select *,b.*
from tb_test a
cross apply dbo.Udf_Keywords_Split(a.au) b
如图：

使用函数如下：
CREATE FUNCTION [dbo].[Udf_Keywords_Split]
(
    -- Add the parameters for the function here
    @KeywordsListString NVARCHAR(MAX)
)
RETURNS
@KeywordsList TABLE
(
    -- Add the column definitions for the TABLE variable here
    OrderNum int,
    Keywords NVARCHAR(MAX)
)
AS
BEGIN
    -- Fill the table variable with the rows for your result set
    DECLARE @EndFlag INT
    DECLARE @KeywordsCount INT
    DECLARE @KeywordsListStr NVARCHAR(MAX)
   
    SET @EndFlag=LEN(@KeywordsListString)-LEN(REPLACE(@KeywordsListString,';',''))+1
    SET @KeywordsCount=0
    SET @KeywordsListStr=ltrim(rtrim(@KeywordsListString))
   
    WHILE @EndFlag>0 AND @KeywordsListStr<>''
    BEGIN
        IF CHARINDEX(';',@KeywordsListStr)>0
        
            BEGIN
                DECLARE @KeywordsStr NVARCHAR(MAX)
               
               
                SET @KeywordsStr=LEFT(@KeywordsListStr,CHARINDEX(';',@KeywordsListStr)-1)
               
               
                SET @EndFlag=@EndFlag-1
                SET @KeywordsCount=@KeywordsCount+1
               
                SET @KeywordsStr=ltrim(replace(@KeywordsStr,CHAR(10),''))
                SET @KeywordsStr=ltrim(replace(@KeywordsStr,CHAR(13),''))
                        
                INSERT INTO @KeywordsList(OrderNum,Keywords)
                VALUES(@KeywordsCount,@KeywordsStr)
                SET @KeywordsListStr=RIGHT(@KeywordsListStr,len(@KeywordsListStr)-CHARINDEX(';',@KeywordsListStr))
            END
        ELSE
            BEGIN
            
                    SET @EndFlag=@EndFlag-1
                    SET @KeywordsCount=@KeywordsCount+1
                    
                    SET @KeywordsListStr=ltrim(replace(@KeywordsListStr,CHAR(10),''))
                    SET @KeywordsListStr=ltrim(replace(@KeywordsListStr,CHAR(13),''))
               
                    INSERT INTO @KeywordsList(OrderNum,Keywords)
                    VALUES(@KeywordsCount,ltrim(@KeywordsListStr))
            END
    END
    RETURN
END

怎样写个SQL语句将输出样式如下的数据

ID    AU1        AU2        AU3           ........    AU(n)
1    Cui, WY    Zhao, SF    Polanowska-Grabowska, R  NAME(n)

n的最大值可以从dbo.Udf_Keywords_Split(a.au)的OrderNum中查询到，当对应ID没有第x个作者时用NULL填充

我看了PIOVT相关的文章，还是不会，请大神们指教，谢谢