INSERT / UPDATE / DELETE、または複数のトリガーを持つことはより良いですか？

Question

1つのテーブルから別のテーブルへの挿入/更新/削除操作をミラーリングする必要があります。 たとえば、Tableaへの挿入をTABLEBにコピーし、TableAに適用されたTableaへの更新、およびTableAからの削除をTABLEBに適用することができます。 それはそれと同じくらい簡単です、tablebは一定の値のための1つの追加列を持っているので、非常に単純なトリガが必要です。

3つの別々のトリガーを書く方が良いか、またはすべての操作を行う1つのトリガーがあるかどうかわかりません。

これは3つのデータベースのためのものです：Sybase ASE、MSSQL、およびOracleでは、その解決策も同様の解決策を維持したい（したがって、すべてのデータベースの場合は3、またはそれらのすべての場合は1）。

は、3つのトリガー対1を持つこと、またはどちらの解決策に実際の利点があるかということです。

Answer 1

Assuming that you actually need a trigger and that table B cannot simply be defined as a view on top of table A or that table B cannot just be defined with a foreign key that references a row in A along with the constant, that A cannot be redefined to add the additional column (potentially with a default value of the constant), one trigger at least lets you keep all the related logic in one place rather than having multiple places that need to be updated when you do something like add a new column to A. But I would be extremely wary of any architecture that involved having two different tables reflecting essentially the same data in both. That violates normalization, it adds to the system's I/O workload, and it makes the whole system more complex.

Answer 2

There's no efficiency to be gained by separating the triggers, other than the loss of efficiency of the trigger execution itself, when trying to determine what the action on Table A was.

IE 3 separate triggers can employ no validation logic to determine what just occurred on Table A, since the trigger being fired itself can behave in a bubble because it knows since it's firing, it was due to single action.

Whereas a 3-in-1 trigger, you must check the status of the virtual deleted and inserted tables and derive the action each and every time it's fired.

If you're not worried about the (admittedly small) performance impact of deriving the "action", or maybe don't even need to know in Table B the "action" that just occurred on Aable A...then I think 1 is perfectly fine.