SQL Server 2022

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create table mytable (
  ArticleId	int,
  CrossArticleId int
);

insert into mytable values
(1,	5),
(5,	10),
(5,	12),
(1,	6),
(6,	10),
(6,	13),
(1,	8),
(8,	10),
(1,	9),
(9,	13),
(9,	15);
11 rows affected

select t2.CrossArticleId
from mytable t1
inner join mytable t2 on t1.CrossArticleId = t2.ArticleId
where t1.ArticleId = 1


CrossArticleId


10

12

10

13

10

13

15


SELECT DISTINCT t2.CrossArticleId
FROM mytable t1
INNER JOIN mytable t2 on t1.CrossArticleId = t2.ArticleId
WHERE t1.ArticleId = 1


CrossArticleId


10

12

13

15