如何检查表中不同行的值

这里有几个选项，哪个性能更好取决于您的测试，而不是我(特别是当我不知道您有什么索引时)。一个使用条件聚合来检查所有值是否都在那里，另一个使用子查询并计算DISTINCT值(因为我不知道是否可能有重复的分类):

SELECT *
INTO dbo.YourTable
FROM (VALUES(123,1),
(123,2),
(123,3),
(123,4),
(657,1),
(657,3),
(657,4))V(ID,Classification);
GO
CREATE CLUSTERED INDEX CI_YourIndex ON dbo.YourTable (ID,Classification);
GO
SELECT ID,
Classification,
CASE WHEN COUNT(CASE YT.Classification WHEN 1 THEN 1 END) OVER (PARTITION BY ID) > 0
AND COUNT(CASE YT.Classification WHEN 2 THEN 1 END) OVER (PARTITION BY ID) > 0
AND COUNT(CASE YT.Classification WHEN 3 THEN 1 END) OVER (PARTITION BY ID) > 0 
AND COUNT(CASE YT.Classification WHEN 4 THEN 1 END) OVER (PARTITION BY ID) > 0 THEN 1 ELSE 0
END AS Flag
FROM dbo.YourTable YT;
GO
SELECT ID,
Classification,
CASE (SELECT COUNT(DISTINCT sq.Classification)
FROM dbo.YourTable sq
WHERE sq.ID = YT.ID
AND sq.Classification IN (1,2,3,4)) WHEN 4 THEN 1 ELSE 0
END AS Flag
FROM dbo.YourTable YT;
GO
DROP TABLE dbo.YourTable;