SQL Server using triggers and geting rid of ON DELETE CASCADE

问题

I have 2 tables, A and B.

Table B has a foreign key pointing to primary key of table A. The foreign key on table B has ON DELETE CASCADE, so the corresponding records from B is deleted when a record from A is deleted.

My requirement is to track all added/updated/deleted records in history tables. I have trigger on each table to insert the records into history tables(AHistories and BHistories tables).

I do not like the order ON DELETE CASCADE deletes the records. Trigger A is executed after trigger B, so I have to work around to get the ID of AHistory into BHistory record.

I am wanting to get rid of ON DELETE CASCADE and perform Delete on the records of B in trigger A then insert the deleted record of B into BHistories there.

To demonstrate the idea, I made the case simple, but I have a few more tables that have a foreign key pointing to the primary key in table A. Personally, I would like if I can specify the order and what I do on delete cascade.

Does this stink as an approach? Any comments are appreciated.

回答1:

As bad as triggers are but sometimes they are the only way to implement complex business requirements. I would do something as follows in the following example PK_ID refers to Primary Key Column.

CREATE TRIGGER tr_Table_A_InsteadOfDelete
ON dbo.TableA
INSTEAD OF DELETE
AS
BEGIN
  SET NOCOUNT ON;

BEGIN TRANSACTION;

    -- Insert into History Table from TableB

    INSERT INTO TABLE_B_History
    SELECT B.*
    FROM TableB B INNER JOIN deleted d
    ON B.PK_ID = d.PK_ID

    -- Delete rows from TableB

      DELETE FROM TableB
        WHERE EXISTS (SELECT 1 
                      FROM deleted 
                      WHERE PK_ID = TableB.PK_ID) 

    -- Insert into History Table from TableA

    INSERT INTO TABLE_A_History
    SELECT A.*
    FROM TableA A INNER JOIN deleted d
    ON A.PK_ID = d.PK_ID

    -- Delete rows from TableA

      DELETE FROM TableA
        WHERE EXISTS (SELECT 1 
                      FROM deleted 
                      WHERE PK_ID = TableA.PK_ID) 

COMMIT TRANSACTION;

END

回答2:

Using triggers for audit purposes is as obvious as it's wrong. If you have sufficient permissions, they can be disabled too easily.

Nevertheless, what you want to do can be achieved with the combination of:

INSTEAD OF DELETE triggers, where you can delete or move rows around in any order;
Disabling nested triggers. This might has unpleasant side effects, if you use triggers for more than just the audit, because it's a database-wide option.

Just don't forget that in such a trigger, you have to manually delete rows from its underlying table, as well.

来源：https://stackoverflow.com/questions/25221925/sql-server-using-triggers-and-geting-rid-of-on-delete-cascade

标签

sql

sql-server

database

Cascade