Question

我们有一个主'用户'表和许多表引用UserId

直接：UserId是子表中的FK或
间接地：'孙子'表中的另一个FK引用子表中的记录，而该表又通过FK约束引用UserID。

现在，如果一切都很完美，删除用户应该与在主表中删除它们一样简单，并且ON CASCADE约束通过其余表将其涟漪。问题是我们不能100％确定引用的每个表中的每个FK关系（直接或间接）是否具有ON CASCADE约束。我们需要一些方法来发出删除并观察SQL Server实际触摸要删除的表。我读了this并尝试了它，但它没有显示任何级联的表 - 只是主表中的条目

以下是我的尝试：

DELETE umt
OUTPUT DELETED.*
FROM [OurAppDb].[dbo].[UserMasterTable] umt
WHERE umt.UserId LIKE 'ABCDABCD-ABCD-ABCD-ABCD-ABCDABCDABCD'

如何查看上述查询将触及的所有表格？

注意：ON CASCADE约束是我们认为在构建每个表时为每个表添加的数据库中的约束。它被添加到一个表上的示例

ALTER TABLE [dbo].[UserEmailPrefs]  
WITH CHECK ADD  CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId])
REFERENCES [dbo].[UserMasterTable] ([UserId])
ON DELETE CASCADE
GO

ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId]
GO

Answer 1

要检查整个数据库中引用UserMasterTable的引用约束，请使用INFORMATION_SCHEMA视图。

SELECT RC.CONSTRAINT_NAME, TU.TABLE_NAME, RC.DELETE_RULE, RC.UPDATE_RULE 
  FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC
  INNER JOIN INFORMATION_SCHEMA.CONSTRAINT_TABLE_USAGE TU
          ON RC.CONSTRAINT_CATALOG = TU.CONSTRAINT_CATALOG 
         AND RC.CONSTRAINT_NAME = TU.CONSTRAINT_NAME
  INNER JOIN INFORMATION_SCHEMA.table_constraints TC 
          ON RC.unique_constraint_name = TC.CONSTRAINT_NAME
  WHERE TC.TABLE_NAME='Users'

这将返回一个针对UserMasterTable的引用约束列表，并为每个引用约束，哪个表引用UserMasterTable，以及ON DELETE和ON UPDATE规则是什么。通过此，您可以快速查看哪些参照约束缺少所需的CASCADE规则。不需要触发快乐。

要将此扩展为“孙子”引用，请再添加两个join子句。要将其扩展到任意数量的级别，请进行递归CTE。

Answer 2

我认为您可以在触发器中执行此操作（分析[inserted]表并搜索从属表）。例如：您可以创建用于存储查询以检测外键链接的表：

IF NOT EXISTS (
        SELECT *
        FROM [sys].tables T
        WHERE T.NAME = 'FKCheck'
        )
    CREATE TABLE FKCheck (
        TableName SYSNAME
        ,ChildTable SYSNAME
        ,QueryText NVARCHAR(MAX)
        )
ELSE
    EXEC('DROP TABLE FKCheck')

然后用从元数据中提取的动态查询填充

;WITH CTE_FKs
AS (
    SELECT FK.NAME
        ,OBJECT_name(fk.parent_object_id) AS ChildTable
        ,OBJECT_name(fk.referenced_object_id) AS ParentTable
        ,delete_referential_action_desc AS DeleteAction
        ,MainTable.NAME AS MainTableColumn
        ,ChildObject.NAME AS ChildColumnName
    FROM sys.foreign_keys FK
    INNER JOIN sys.foreign_key_columns FKC ON FKC.constraint_object_id = FK.object_id
    INNER JOIN sys.columns AS ChildObject ON ChildObject.object_id = FKc.parent_object_id
        AND FKC.parent_column_id = ChildObject.column_id
    INNER JOIN sys.columns AS MainTable ON MainTable.object_id = FK.referenced_object_id
        AND MainTable.column_id = FKC.referenced_column_id
    )
    ,CTE_Tables
AS (
    SELECT DISTINCT C.NAME
        ,C.ParentTable
        ,C.DeleteAction
        ,C.ChildTable
    FROM [CTE_FKs] C
    )
INSERT INTO [dbo].[FKCheck] (
    TableName
    ,ChildTable
    ,QueryText

    )
SELECT C.ParentTable,C.ChildTable
    ,'IF EXISTS (select 1 from inserted INNER JOIN  ' + QUOTENAME(C.ChildTable) + ' ON ' + STUFF((
            SELECT ' AND inserted.' + QUOTENAME(C2.MainTableColumn) + ' = ' + + QUOTENAME(C2.ChildTable) + '.' + QUOTENAME(C2.ChildColumnName)
            FROM CTE_FKs C2
            WHERE C2.ParentTable = C.ParentTable
                AND C2.NAME = C.NAME
            FOR XML PATH('')
                ,TYPE
            ).value('.', 'nvarchar(MAX)'), 1, 4, '') + ')
 RAISERROR(''Relation with ' + QUOTENAME(C.ChildTable) +':'+ CASE C.DeleteAction
        WHEN 'CASCADE'
            THEN ' data will be deleted'
        WHEN 'SET_NULL'
            THEN ' set as NULL'
        WHEN 'NO_ACTION'
            THEN ' no default action'
        ELSE 'Unknown'
        END + ''')'
FROM [CTE_Tables] C

您在表格中的查询将如下所示：

 IF EXISTS (select 1 from inserted INNER JOIN  [UserEmailPrefs] ON  inserted.[UserId] = [UserEmailPrefs].[UserId])
 RAISERROR('Relation with [UserEmailPrefs]: no default action')
IF EXISTS (select 1 from inserted INNER JOIN  [UserEmail] ON  inserted.[UserId] = [UserEmail].[UserId])
 RAISERROR('Relation with [UserEmail]: set as NULL')

然后在触发器中，您可以执行查询以打印消息：

 DECLARE @TableName SYSNAME = 'UserMasterTable';
    DECLARE @sSQL NVARCHAR(MAX) = '';

    SELECT @sSQL += F.QueryText + CHAR(10)
    FROM FKCheck F
    WHERE F.TableName = @TableName;
EXEC(@sSQL)
ROLLBACK

如果您需要分析更多“远程”表，则需要在FKCheck表中遍历层次结构。

为具有ON CASCADE约束的记录预览SQL DELETE

2 个答案: