SQL Server 2017

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create table your_table (
 id int identity primary key, 
 fieldname varchar(100)
);
insert into your_table (fieldname) values
('0001, ABCD1234;0002, EFGH432562;0003, IJKL1345hsth;');
1 rows affected

CREATE FUNCTION dbo.SplitOrdered
(
    @list    nvarchar(max), 
    @delim   nvarchar(10)
)
RETURNS TABLE 
WITH SCHEMABINDING 
AS 
RETURN
(
  WITH w(n) AS (SELECT 0 FROM (VALUES (0),(0),(0),(0)) w(n)),
       k(n) AS (SELECT 0 FROM w a, w b),
       r(n) AS (SELECT 0 FROM k a, k b, k c, k d, k e, k f, k g, k h),
       p(n) AS (SELECT TOP (COALESCE(LEN(@list), 0)) 
                ROW_NUMBER() OVER (ORDER BY @@SPID) -1 FROM r),
       spots(p) AS 
       (
         SELECT n FROM p 
         WHERE (SUBSTRING(@list, n, LEN(@delim + 'x') - 1) LIKE @delim OR n = 0)
       ),
       parts(p,val) AS 
       (
         SELECT p, SUBSTRING(@list, p + LEN(@delim + 'x') - 1, 
           LEAD(p, 1, 2147483647) OVER (ORDER BY p) - p - LEN(@delim)) 
         FROM spots AS s
       )
       SELECT listpos = ROW_NUMBER() OVER (ORDER BY p), 
              Item    = LTRIM(RTRIM(val))
         FROM parts
);
    ;WITH x AS 
    (
      SELECT id, listpos, 
        codes = LEFT(Item, COALESCE(NULLIF(CHARINDEX(',', Item),0),1)-1)
      FROM dbo.your_table
      CROSS APPLY dbo.SplitOrdered(fieldname, ';') AS c
    )
    SELECT id, codes = (
      (SELECT x2.codes + ' '
        FROM x AS x2
         WHERE x2.id = x.id
         ORDER BY x2.listpos
         FOR XML PATH(''), TYPE).value(N'./text()[1]', N'nvarchar(max)')
    )
    FROM x GROUP BY id;


id
codes


1
0001 0002 0003