Re: Pre-DML trigger vs Foreign keys

[Rick James]

What do you want the trigger/FK to do?

Why do you want to do it with a trigger/FK instead of being in direct control in your app?

If you are doing fewer than 100 queries/sec, performance is a non-issue.

Back to your question... Here are some principles to use to figure out the answer:
* A FK will reach into the 'other' table to check for the existence/absence of the corresponding row. This takes some effort. If the dataset is big enough, this is likely to be a disk hit.
* A TRIGGER must interpretively perform the instructions indicate. If these are hitting some other table, then the cost of that must be considered.

It sounds like you are suggesting simulating a FK using a Trigger. As a general principle, a simulation is going to be slower than the 'real thing'.