It can be shown that a subset of the presented operators (specifically the select, project, union, difference and product) are adequate, or complete, to describe the other operators (for example join, intersection etc).
Ni inaweza kuonyeshwa kwamba subset ya kampuni za aliwasilisha (hasa kuchagua, mradi, muungano, tofauti na bidhaa) ni wa kutosha, au kamili, kuelezea watendaji wengine (kwa mfano kujiunga, makutano nk).