Be explicit of where the constraints are.

railties/guides/source/migrations.textile

@@ -891,7 +891,7 @@ which models can enforce data integrity. The +:dependent+ option on associations
 allows models to automatically destroy child objects when the parent is
 destroyed. Like anything which operates at the application level, these cannot
 guarantee referential integrity and so some people augment them with foreign key
-constraints.
+constraints in the database.
 
 Although Active Record does not provide any tools for working directly with such
 features, the +execute+ method can be used to execute arbitrary SQL. You could