Question

SELECT *
FROM [dbo].[CountData] CD
INNER JOIN [dbo].[Count] C ON CD.CountId = C.CountId
LEFT JOIN [dbo].[Leg] L ON C.IntersectionId = L.IntersectionId AND CD.ApproachId = L.ApproachId 
WHERE L.IntersectionId IS NULL

如何重写此查询，以使不涉及LEFT JOIN。最终目标是要有一个可以作为索引视图接受的查询：https://www.brentozar.com/archive/2013/11/what-you-can-and-cant-do-with-indexed-views/（不允许左联接）

注意：不允许子查询

Answer 1

您可以使用NOT EXISTS重写它：

SELECT *
FROM [dbo].[CountData] CD
JOIN [dbo].[Count] C
  ON CD.CountId = C.CountId
WHERE NOT EXISTS (SELECT 1 FROM [dbo].[Leg] L
                  WHERE C.IntersectionId = L.IntersectionId 
                    AND CD.ApproachId = L.ApproachId)

将左联接重写为索引视图的where子句

1 个答案: