Question

In my database I have certain data that is important to the functioning of the app (constants, …). And I have test data that is being generated by testing the site. As the test data is expendable it delete it regularly. Unfortunately the two types of data occur in the same table so I cannot do a delete from T but I have to do a delete from T where IsDev = 0.

How can I make sure that I do not accidentally delete the non-dev data by forgetting to put the filter in? If that happens I have to restore from a production backup which is wasting my time. I would require some sort of foreign key like behavior that fails a delete when a certain condition is met. This would also be useful to ensure that my code does not do anything harmful due to a bug.

Answer 1

Well, you could use a trigger that throws an exception if any of the records in the deleted meta-table have IsDev = 1.

CREATE TRIGGER TR_DEL_protect_constants ON MyTable FOR DELETE AS
BEGIN
    IF EXISTS(SELECT 1 FROM deleted WHERE IsDev <> 0)
    BEGIN
        ROLLBACK
        RAISERROR('Can''t delete constants', 1, 16)
        RETURN
    END
END

I’m guessing a bit on the syntax, but you get the idea.