Your database is is the state of your system. Guard it!

I just ran into severe data corruption at a large client because a programmer four years ago wrote an empty catch block. The system would open a transaction, hit a fault, roll back, then continue writing to the database as if it’s still in the context of the transaction.

I spent some time trying to pin down exactly what it did, and found that many writes went through because of a missing foreign key constraint.

In short: if a particular table of minor importance had a foreign key constraint, there would have been no damage whatsoever, because it would have faulted immediately after the rollback.

You can’t rig up a constraint against every dumb write. But you can rig them up against some of the dumb writes. And sometimes that’s enough.