thanks oddz and rudy,
I don't have any scripting established which would do that.
Likely, my question arose from over-thinking. I had a concern that if someone were to find a way to delete a table or some records, the on delete cascade constraint would remove data through numerous tables. I wanted to find a balance between utilising constraints and preventing such a deletion.
I do have the connections set up with the appropriate permissions. And I have the scripts (which allow user input), written only to allow sanitised data input. Indeed all params passed between scripts is sanistised or rejected. Those which don't invite/support user-generated input are connected with read only privileges so messing with params being passed from page to page, won't input anything.
I suppose I should only use a fk constraint which allows on update cascade given that, deleting could be performed on each table, from child upwards. Indeed, preventing deletion by archiving the 'old' data to another table might be better too.
Is my concern explained well enough? Does it sound like I have addressed or am at least aware of the issues to be secured and addressed?