Subject foreign key vs triggers
Author Evelyne Girard
Is there a way to make a foreign key lock the records the same way triggers
do ?

If I have a foreign key and I update a value (not the key field) on the
referenced table, I cannot insert a record for this key field in the
"refererring" table (I get a lock conflict).

On the other side, if I implement the same integrity constraint with 3
triggers( on referenced_table update, delete and on referring_table update
or insert), I can insert the record without any trouble.