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by Jiří {x2} Činčura

How dumb the instead of triggers on MS SQL are???

23 Jul 2009 MS SQL Server

Shortly: Very.

I hate the idea of instead of triggers and I made a couple of blog posts several times. And even worse is the implementation behavior on MS SQL. And the cascade constraints are bad too.

Let’s suppose this simple definition.

create table master(id int primary key, foo nvarchar(20));
create table detail(id int primary key, id_master int not null, bar nvarchar(20));
alter table detail add foreign key (id_master) references master(id) on delete cascade;

Nothing special. Works fine, no problems expected. Until you try to define instead of delete trigger on detail table. I.e.

create trigger tr_test on detail
instead of delete as
  select 1;
  -- now the fun begins

You get an nice error: Cannot create INSTEAD OF DELETE or INSTEAD OF UPDATE TRIGGER 'tr_test' on table 'detail'. This is because the table has a FOREIGN KEY with cascading DELETE or UPDATE.. What the hell??? :o Why?

Again I got a direct proof, that in this area the MS SQL is wrong, very wrong. I would be willing to accept the limitation when I’ll be doing there some master table manipulation (yes, as I said, cascade constraints are bad too). But this? I can hardly believe my eyes. The trigger is almost empty. Or am I missing someting on backround that limits this to work?

Another “feature” that makes me love Firebird more.