Konwersja ciągu rozdzielanego przecinkami na wiele kolumn w serwerze sql

Możesz to zobaczyć w SQL Fiddle:http://sqlfiddle.com/#!3/ 8c3ee/32

Oto sedno tego:

with parsed as (
  select
  commasepa,
  root.value('(/root/s/col[@name="X"])[1]', 'varchar(20)') as X,
  root.value('(/root/s/col[@name="Y"])[1]', 'varchar(20)') as Y,
  root.value('(/root/s/col[@name="Z"])[1]', 'varchar(20)') as Z,
  root.value('(/root/s/col[@name="A"])[1]', 'varchar(20)') as A,
  root.value('(/root/s/col[@name="B"])[1]', 'varchar(20)') as B,
  root.value('(/root/s/col[@name="C"])[1]', 'varchar(20)') as C,
  root.value('(/root/s/col[@name="D"])[1]', 'varchar(20)') as D
FROM
(
select
   commasepa,
   CONVERT(xml,'<root><s><col name="' + REPLACE(REPLACE(COMMASEPA, '=', '">'),',','</col></s><s><col name="') + '</col></s></root>') as root
FROM
  samp
) xml
)
update 
  samp
  set
  samp.x = parsed.x,
  samp.y = parsed.y,
  samp.z = parsed.z,
  samp.a = parsed.a,
  samp.b = parsed.b,
  samp.c = parsed.c,
  samp.d = parsed.d
from
  parsed
where
  parsed.commasepa = samp.commasepa;

Pełne ujawnienie - jestem autorem sqlfiddle.com

Działa to, najpierw konwertując każdy ciąg przecinków na obiekt XML, który wygląda tak:

<root>
 <s>
  <col name="X">1</col>
 </s>
 <s>
  <col name="Y">2</col>
 </s>
  ....
</root>

Po uzyskaniu ciągu w tym formacie używam opcji xquery obsługiwanych przez SQL Server 2005 (i nowsze), czyli .value('(/root/s/col[@name="X"])[1]', 'varchar(20)') część. Każdą z potencjalnych kolumn wybieram indywidualnie, więc są one znormalizowane i wypełniane, gdy są dostępne. W tym znormalizowanym formacie definiuję zestaw wyników za pomocą wyrażenia Common Table Expression (CTE), które nazwałem „przeanalizowanym”. To CTE jest następnie łączone z powrotem w instrukcji aktualizacji, dzięki czemu wartości mogą być wypełnione w oryginalnej tabeli.