The Delete command deletes all the currently selected entities and all other entities that use them.
Caution: It is important to keep in mind that deleting a particular entity may trigger a sort of "chain" reaction that will delete all other entities using it.
Note that a block entity is bounded by (i.e. "uses") domain entities which in turn are bounded by (i.e. "use") connector entities. Therefore, if you delete a connector entity, all the domains using that particular connector will be deleted as well. Subsequently, all the blocks using those now non-existent domains will also be deleted. On the other hand, note that deleting a block entity will not delete its bounding domains and connectors (the block "uses" the domains and connectors and not the other way around) unless the Delete Special command is used.
Also note that database models and quilts need underlying database surfaces as part of their definition and not the other way around. Therefore, deleting a database surface will cause the database quilt and stand alone model entities defined by it (i.e. "using it") to be deleted as well. On the other hand, if a database model is deleted, its associated quilts will be deleted as well but the underlying database surfaces will remain (unless the Delete Special command is used).
A special case is presented when deleting database entities that have grid entities constrained to them (review the On Database Entities section for more details). In this case, a dialog will appear stating that the associated grid entities are about to become unconstrained (see image below). The options in the dialog will allow you to decide how to proceed: