Kodi Boyce-Codd Form Formal (BCNF) Ndi Chiyani?

BCNF imachepetsanso zochepa zomwe zimapangitsa kuti chiwerengero cha data chiwonjezeke

Cholinga cha Fomu ya Boyce-Codd Normal (BCNF) ndichokulitsa umphumphu wa data pakukonza ndondomeko ndi matebulo a deta yolumikizana kuti athe kukwaniritsa chiwerengero cha chidziwitso. Kuyimira chidziwitso kumapezeka pamene pali kukhazikitsidwa mgwirizano pakati pa matebulo ndi pamene matebulo atanthauzira malamulo kuti mazikowa athe kusintha komanso kusunga deta.

Zolinga za normalization zamasamba ndizochotsa deta yopanda malire ndikuonetsetsa kuti kudalira deta kumawoneka bwino.

Mndandanda wa masitepe umawoneka ngati deta yomweyi siyikusungidwa mu tebulo limodzi komanso pamene deta yokhayokhayo imasungidwa patebulo.

Chiyambi cha Fomu ya Boyce-Codd Yowiririka

Potsatira ndondomeko yambiri yotsimikiziranso kuti zolembazo ndizokhazikika. Malangizo awa amatchulidwa ngati mawonekedwe achibadwa ndipo amawerengedwa kuyambira mmodzi mpaka asanu. Dongosolo lothandizira limafotokozedwa ngati lokhazikika ngati likukumana ndi mitundu itatu yoyamba: 1NF, 2NF, ndi 3NF.

BCNF inalengedwa monga chongowonjezera ku mawonekedwe achiwiri, kapena 3NF, mu 1974 ndi Raymond Boyce ndi Edgar Codd. Amunawa anali kugwira ntchito kuti apange masanjidwe a mndandanda wamakono omwe amachepetseratu ziphuphu zambiri n'cholinga chochepetsera nthawi yolemba. Fomu yachiwiri yachiwiri imachotsa zipilala zomwe sizidalira makiyi apamwamba kuphatikizapo kukambirana zotsatila zoyamba. BCNF, yomwe nthawi zina imatchedwa 3.5NF, imakwaniritsa zofunikira zonse za 3NF ndipo imafuna kuti makiyiwo asakhale ndi chidaliro pazinthu zina mu tebulo.

Pa nthawi ya kulengedwa kwa BCNF, Boyce anali mmodzi mwa anthu otsogolera kwambiri a Structured English Query Language (SQL), zomwe zinawathandiza kuti azigwiritsa ntchito njira ya Codd. Mu chitsanzo ichi, Codd inanena kuti zovuta zowonongeka zazitsulo zingathe kuchepetsedwa, zomwe zikutanthauza kuti mafunso angakhale amphamvu komanso osintha.

Pogwiritsa ntchito mfundo zake zachinsinsi, Codd inafotokoza 1NF, 2NF, ndi 3NF malangizo. Anagwirizana ndi Boyce kuti afotokoze BCNF.

Othandizira Makhadi ndi BCNF

Mphindi yachindunji ndi mzere kapena kuphatikizapo zipilala patebulo lomwe limapanga fungulo lapaderalo m'databata. Kuphatikizidwa kwa makhalidwe kungagwiritsidwe ntchito pozindikira mbiri yachinsinsi popanda kutchula deta iliyonse. Gome lirilonse lingakhale ndi mafungulo ambiri ovomerezeka, omwe amatha kukhala ofunikira kwambiri. Gome liri ndi choyika chimodzi chokha.

Makiyi oyenera ayenera kukhala apadera.

Chiyanjano chiri mu BCNF ngati chowona chirichonse chiri chofunika kwambiri. Ganizirani za tebulo lachinsinsi limene limasunga zambiri za ogwira ntchito ndipo liri ndi malingaliro , , , ndi