Question

以下查询需要花费大量时间才能将结果返回到两个不同的数据库中。有没有办法简化这个查询？

WITH tblParent AS 
(
    SELECT * 
    FROM REFERENCES 
    WHERE referenced_id = 208593

    UNION ALL

    SELECT REFERENCES.* 
    FROM REFERENCES
    JOIN tblParent ON REFERENCES.referenced_id = tblParent.entity_Id
)
SELECT DISTINCT(entity_Id)
FROM tblParent
WHERE entity_Id <> 208593 AND field_type = 'ChildField'
OPTION(MAXRECURSION 5)

Answer 1

这应该简化它：

<figure>
    <img src="http://www.innomate.com/application/files/4514/8474/3363/front01.png" />
    <figcaption>Testing</figcaption>
</figure>

通过检查c值，很明显它是一个子值。我假设这个文本对所有孩子都有field_type ='ChildField'。

（REFERENCES是保留字，DISTINCT不是函数）

Answer 2

由于您只对子entityId感兴趣，因此只需在递归CTE中选择所需的字段即可。

WITH tblParent AS (
    SELECT entity_Id, referenced_id as baseId
    FROM [REFERENCES]
    WHERE referenced_id = 208593

    UNION ALL

    SELECT t.entity_Id, cte.baseId
    FROM tblParent cte
    JOIN [REFERENCES] t 
      ON (t.referenced_id = cte.entity_Id 
          AND t.entity_Id <> cte.baseId -- to avoid a circular reference
          )
    WHERE t.field_type = 'ChildField'
)
SELECT DISTINCT entity_Id
FROM tblParent
WHERE entity_Id <> baseId 
OPTION(MAXRECURSION 5)

你可能想要仔细检查一下reference_id是否有索引。

简化SQL Server查询

2 个答案: