Functional Dependencies Batsira Kudzivisa Kudzokorora Data
Kushanda kunoshanda mune imwe database kunogadzirisa chinetso chezvipingamupinyi pakati pezvinhu. Izvi zvinoitika kana chimwe chiitiko muhukama hwakasarudzwa chimwe chinhu. Izvi zvinogona kunyorwa A -> B zvinoreva kuti "B inoshanda zvichienderana neA" Izvo zvinonziwo hupenyu hwekuchengetedzwa kwemashoko .
Muukama uhwu, A inotarisa kukosha kweB, apo B iripo A.
Chikonzero nei kushandiswa kwekushanda kwakakosha muDatabase Design
Kushanda kunomiririra kunobatsira kuchengetedza kuvimbika kwe data.Cherechedza tafura Vashandi vanotora zvinhu zvinosanganisira Social Security Number (SSN), zita, zuva rokuberekwa, kero nezvimwe zvakadaro.
Chirevo cheSnN chichagadza kukosha kwezita, zuva rekuberekwa, kero uye pamwe nemamwe maitiro, nokuti nhamba yekuchengetedzwa kwevanhu yakasiyana, apo zita, zuva rokuberekwa kana kero risingave. Tinogona kuinyora sezvizvi:
SSN -> zita, zuva rokuzvarwa, kero
Saka, zita, zuva rokuberekwa nekero rakashanda rinotsigirwa neSNN. Zvisinei, mashoko anotevera (zita -> SSN) haasi echokwadi nokuti vakawanda vanoshanda kamwe chete vanogona kuva nezita rimwe chete asi havazombovi neSNS imwecheteyo. Isa imwe, nzira yakawedzerwa, kana tichiziva kukosha kwehuwandu hweSSSN, tinogona kuwana kukosha kwezita, zuva rekuberekwa nekero. Asi kana isu pane kudaro tichiziva kukosha kwezita rega zita, hatigone kuziva SSN.
Rutivi rworuboshwe rwehutano hunoshanda runogona kusanganisira zvinopfuura imwechete. Ngatiti tine bhizinesi rine nzvimbo dzakawanda. Tingave tafura yekushanda Employee nemafungiro evashandi, musoro, dhipatimendi, nzvimbo uye maneja.
Muranda anosarudza nzvimbo yaanoshanda, saka pane kuvimba:
mushandi -> nzvimbo
Asi nzvimbo inogona kuva nemenenja imwe chete, saka mushandi uye dhipatimendi pamwe vanoona mutungamiriri:
mushandi, dhipatimendi -> maneja
Functional Dependency uye Normalization
Kushanda kunomiririra kunobatsira kune izvo zvinonzi database yekusimudzira , iyo inogonesa duramaidzo yedhesi uye inoderedza kuderedzwa kwe data. Pasina kumira, hapana chivimbo chokuti data iri mune database yakarurama uye yakavimbika.