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).
Maaari itong i-ipinapakita na ang isang subset ng mga iniharap operator (partikular na ang piliin, proyekto, union, pagkakaiba at produkto) ay sapat, o kumpleto, upang ilarawan ang iba pang mga operator (halimbawa sumali, intersection atbp).