Question

我使用Entity Framework从我的模型中生成我的表，并且我不时地遇到多个级联路径的问题。 e.g：

引入FOREIGN KEY约束＆＃39; FK_dbo.SurveyorSurveys_dbo.Surveys_Survey_ID＆＃39;桌子上＆＃39; SurveyorSurveys＆＃39;可能导致循环或多个级联路径。

我发现在这个新表的级联路径所在的位置非常耗时，因此我可以删除其中一个级联删除。我认为如果我可以在系统表上运行查询，向我展示所涉及的完整路径，那将非常有用。有没有人知道如何做到这一点？

例如我有这个sql：

SELECT
    ro.name referenced_object,
    po.name parent_object,
    fk.name foreign_key
FROM sys.foreign_keys fk
    INNER JOIN sys.all_objects po
    ON fk.parent_object_id = po.object_id
    INNER JOIN sys.all_objects ro
    ON fk.referenced_object_id = ro.object_id
WHERE delete_referential_action_desc = 'CASCADE'
and (po.name = 'Surveys' or po.name = 'Surveyors'')
ORDER BY ro.name

但是这只会让我在层次结构中达到一个级别，在更高级别删除级联删除可能会更好，所以我最终调整并重新运行sql，直到我找到完整路径

Answer 1

这通常与recursive query有关。

首先澄清一下sys.all_objects中的列名：

parent_object_id是指拥有外键的对象，因此它不是关系中的父级，而是孩子。

referenced_object_id是关系中的父母。

知道了这一点，我们可以编写一个递归查询，通过将前一级别的子级与后续级别中的父级连接来收集外键关系树：

WITH [Cascades] AS( SELECT fk.referenced_object_id AS [RootId], fk.parent_object_id AS [ChildId], fk.referenced_object_id AS [ParentId], fk.name foreign_key, 1 AS [Level] FROM sys.foreign_keys fk WHERE delete_referential_action_desc = 'CASCADE' UNION ALL SELECT [Cascades].[RootId], fk.parent_object_id, fk.referenced_object_id, fk.name foreign_key, [Cascades].[Level] + 1 FROM sys.foreign_keys fk INNER JOIN [Cascades] ON [Cascades].[ChildId] = fk.referenced_object_id WHERE delete_referential_action_desc = 'CASCADE' ) SELECT [root].Name AS [Root], po.Name AS [Parent], co.Name AS [Child], foreign_key, cs.[Level] FROM [Cascades] cs INNER JOIN sys.all_objects [root] ON cs.[RootId] = [root].object_id INNER JOIN sys.all_objects po ON cs.ParentId = po.object_id INNER JOIN sys.all_objects co ON cs.ChildId = co.object_id WHERE [root].name = 'Surveys' ORDER BY [Root], [Parent], [Level], [Child]

如果我在简单的树级层次结构中执行查询，则输出为：

Root Parent Child foreign_key Level ----------------------------------- A A B1 FK_B1_A 1 A A B2 FK_B2_A 1 A B1 C FK_C_B1 2

Answer 2

替代sql基于Gert的优秀答案。这个允许我指定叶子并显示每行的完整级联路径

WITH Cascades
AS (SELECT
    fk.parent_object_id,
    fk.referenced_object_id,
    fk.name foreign_keys,
    CAST(ro.name + ' -> ' + po.name AS nvarchar(256)) path,
    1 AS level
FROM sys.foreign_keys fk
    INNER JOIN sys.all_objects po
    ON fk.parent_object_id = po.object_id
    INNER JOIN sys.all_objects ro
    ON fk.referenced_object_id = ro.object_id
WHERE delete_referential_action_desc = 'CASCADE'
-- specifying leaf instead of root:
AND po.name IN ('Surveys', 'Surveyors', 'surveyorsurveys') 
UNION ALL SELECT
    fk.parent_object_id,
    fk.referenced_object_id,
    CAST(fk.name + ' -> ' + Cascades.foreign_keys as nvarchar(128)),
    CAST(ro.name + ' -> ' + cascades.path AS nvarchar(256)),
    cascades.level + 1
FROM sys.foreign_keys fk
    INNER JOIN sys.all_objects po
    ON fk.parent_object_id = po.object_id
    INNER JOIN sys.all_objects ro
    ON fk.referenced_object_id = ro.object_id
    INNER JOIN cascades
    ON cascades.referenced_object_id = fk.parent_object_id
WHERE delete_referential_action_desc = 'CASCADE')
SELECT
    path,
    foreign_keys,
    level
FROM Cascades
ORDER BY path

查询多个级联路径的系统表

2 个答案: