Le mithetho emibili elula izosiza normalizing imininingwane yakho
Ifomu Lokuqala Elijwayelekile (1NF) libeka imithetho eyisisekelo yedatha ehleliwe:
- Khipha amakholomu okuphinda avela kuthebula elifanayo.
- Dala amathebula ahlukene eqenjini ngalinye lemininingwane ehlobene bese uthola irowu ngalinye ngekholomu eyingqayizivele (ukhiye oyinhloko).
Yisho ukuthini le mithetho uma ucabangela ukuklanywa kwe-database? Empeleni kulula kakhulu.
1. Ukuqeda ukuphindaphinda
Umthetho wokuqala ubeka ukuthi akumelwe sibuyele idatha ngaphakathi komugqa ofanayo wetafula. Phakathi komphakathi wedatha, lo mbono ubizwa ngokuthi i-athomu yetafula. Amathebula avumelana nalo mthetho athiwa i-athomu. Ake sihlole lesi simiso ngesibonelo se-classic: itafula ngaphakathi kwedatha yolwazi lwabantu elondoloza ubuhlobo bomphathi. Ngenhloso yesibonelo sethu, sizobeka umthetho webhizinisi ukuthi imenenja ngayinye ingaba neyodwa noma abaningi abangaphansi kwabo ngenkathi omunye ongaphansi engase abe nomphathi oyedwa kuphela.
Intuitively, uma udala uhlu noma ispredishithi ukulandelela lolu lwazi, singadala itafula ngezinkambu ezilandelayo:
- Umphathi
- Okuphansi1
- Okuphansi2
- Okuphansi3
- Okuphansi4
Noma kunjalo, khumbula umthetho wokuqala owenziwe ngu-1NF: Khipha amakholomu okuphinda avela kuthebula elifanayo. Ngokusobala, amakholomu aphansi1-aphansi4 aphindaphindiwe. Thatha isikhashana uphinde ucabange ngezinkinga eziphakanyiswe ngalesi simo. Uma imenenja inomuntu oyedwa kuphela, amakholomu aphansi aphansi -4 alahlekelwa isikhala esilondolozwayo (impahla eyigugu yedatha). Ngaphezu kwalokho, ake ucabange ukuthi umphathi usuphethe kanjani abangaphansi kuka-4 - kwenzekani uma ethatha esinye isisebenzi? Isakhiwo sonke setafula sidinga ukuguqulwa.
Kuleli phuzu, umqondo wesibili okhanyayo uvame ukuvela kumakhomitha e-database: Asifuni ukuba nekholomu engaphezu kweyodwa futhi sifuna ukuvumela inani eliguquguqukayo lokugcina idatha. Ake sizame okufana nalokhu:
- Umphathi
- Abangaphansi
Futhi insimu engaphansi iqukethe okufakiwe okuningi efomu elithi "Mary, Bill, Joe."
Lesi sombululo siseduze, kodwa futhi asikho emkhakheni. Ikholomu elingaphansi lingamaphutha futhi aliwona i-athomu. Kwenzekani uma sidinga ukwengeza noma ukususa ongaphansi? Sidinga ukufunda nokubhala konke okuqukethwe kwetafula. Lokhu akuyona into enkulu kulokhu, kodwa kuthiwani uma umphathi oyedwa enezisebenzi eziyikhulu? Futhi, kuyinkimbinkimbi inqubo yokukhetha idatha kusuka ku-database kumbuzo wesikhathi esizayo.
Nayi ithebula eligcwalisa umthetho wokuqala we-1NF:
- Umphathi
- Ngaphansi
Kulesi simo, ngamunye ongaphansi unencazelo eyodwa, kodwa abaphathi bangaba nokufaka okuningi.
2. Thola Isihluthulelo Esiyinhloko
Manje, kuthiwani ngomthetho wesibili: bona umugqa ngamunye ngekholomu ehlukile noma isethi yamakholomu ( ukhiye oyinhloko )? Ungase ubuke etafuleni elingenhla futhi ukhombise ukusebenzisa ikholomu elingaphansi njengekhibhodi eyinhloko. Eqinisweni, ikholomu elingaphansi liyisihluthulelo esihle sokhiye oyinhloko ngenxa yokuthi imithetho yethu yebhizinisi ichaze ukuthi ngamunye ongaphansi angase abe nomphathi oyedwa kuphela. Noma kunjalo, idatha esiyikhethile ukuyibeka etafuleni lethu yenza lokhu kube yisisombululo esingaphansi kwesimo esihle. Kwenzekani uma siqasha omunye umsebenzi okuthiwa uJim? Sigcina kanjani ubudlelwane bakhe-ukuphathwa okungaphansi kwe-database?
Kungcono ukusebenzisa isihlonzi esiyingqayizivele ngempela (njenge-ID yomsebenzi) njengokhiye oyinhloko . Itafula lethu lokugcina lizobukeka kanje:
- I-ID yomphathi
- I-ID engaphansi
Manje, itafula lethu lisefomu lokuqala evamile! Uma ungathanda ukuqhubeka ufunda ngokujwayelekile, funda ezinye izihloko kulolu chungechunge: