Ukuxhomekeka okunamandla kuDesign Design

Ukuxhomekeka okunamandla kunciphisa ifomu lesine elivamile

Esikhathini sedatha ehlobene, ukuxhomeka kwenzeka lapho ulwazi olugcinwe kuthebula elifanayo le database lugcina ngokukhethekile olunye ulwazi olugcinwe kuthebula elifanayo. Ukuthembela okunomthelela omkhulu kwenzeka lapho ukutholakala komugqa owodwa noma ngaphezulu etafuleni kubonisa ukuba khona komunye noma imigqa eminye etafuleni elifanayo. Faka enye indlela, izimfanelo ezimbili (noma izinsika) etafuleni zizimele, kodwa zombili zixhomeke embonweni wesithathu.

Ukuthembela okunenqwaba yemvelo kuvimbela ifomu elijwayelekile lokujwayelekile elijwayelekile (4NF). Ulwazi olulandelanayo lulandela amafomu amahlanu avamile afaka imihlahlandlela yokukhipha irekhodi. Zivimbela ukungalungi kokubuyekeza nokungahambisani kwedatha. Ifomu lesine elijwayelekile likhuluma ngobuhlobo obuningi kumuntu obunikazi .

Ukusekela okusebenzayo nokuxhomekeka kwe-Multivalued Dependency

Ukuze uqonde ukuthembela okuningi, kuyasiza ukuphinda ubuyekeze ukuthi ukuthembela okusebenzayo kukuphi.

Uma i-X imfanelo ikhetha i-Y, i-Y isebenza ngokweqile ku-X. Lokhu kubhaliwe njenge-X -> Y. Isibonelo, kulaba bafundi Abafundi ngezansi, i-Student_Name inquma ukuthi inkulu:

Lokhu kuncike ekusebenzeni kungabhalwa: Student_Name -> Major . I-Student_Name ngayinye inquma ngokucacile oyedwa Omkhulu, futhi akusekho.

Uma ufuna i-database iphinde ilandele imidlalo lezi zithatha abafundi, ungase ucabange ukuthi indlela elula yokwenza lokhu ukufaka nje enye ikholomu okuthiwa i-Sport:

Inkinga lapha ukuthi uRavi noBheth badlala imidlalo eminingi. Kubalulekile ukwengeza umugqa omusha kuwo wonke umdlalo owengeziwe.

Leli thebula liye laletha ukuthembela okuningi kakhulu ngoba ezinkulu kanye nemidlalo zizimele komunye kodwa zombili zixhomeke kumfundi.

Lesi yisibonelo esilula futhi sibonakala kalula, kepha ukuxhomeka kokuxhumeka kwemali kungaba yinkinga kwi database enkulu, eyinkimbinkimbi.

Ukuthembela okunamatheksthi kubhaliwe X -> -> Y. Kulesi simo:

I-Student_Name -> -> Major
I-Student_Name -> -> Ezemidlalo

Lokhu kufundwa njenge "Student_Name multidetermines Major" ne "Student_Name multidetermines Sport."

Ukuthembela okuningi kakhulu kudinga njalo okungenani izimfanelo ezintathu ngoba kubandakanya okungenani izimfanelo ezimbili ezixhomeke kwisithathu.

Ukuxhomekeka Okunamandla Nokulinganisa

Itafula elincike ekutheni lincike ngokweqile liphula izinga elijwayelekile lokufometha leFomu Eliyisine Elijwayelekile (4NK) ngoba lidala ukubuyiswa okungadingekile futhi kungasiza ekuhambeni kwedatha engahambisani. Ukuze ulethe lokhu ku-4NF, kubalulekile ukuphula lolu lwazi ngamatafula amabili.

Ithebula elingezansi manje lincike ekusebenzeni kwe-Student_Name -> Major, futhi akukho ukuxhomeka okunamandla:

Ngesikhathi leli tafula libuye lithembeke ngokusebenza kwe-Student_Name -> Sport:

Kuyacaca ukuthi ukujwayela kuvame ukubhekwa ngokululaza amathebula adidayo ukuze aqukethe ulwazi oluhlobene nombono owodwa noma isihloko kunokuba uzame ukwenza ithebula elilodwa liqukethe ulwazi olungavamile kakhulu.