Le miyalelo emibini elula izakukunceda ukugcina i-database yakho
Ifom yokuqala yoLuntu (1NF) ibeka imithetho eyimfuneko yedata ehleliweyo:
- Ukuphelisa iikholomu zokuphinda kwitafile enye.
- Yenza amacwecwe ahlukeneyo kwiqela ngalinye leenkcukacha ezihambelanayo kwaye uchaze umqolo ngamnye kunye nekholamu ekhethekileyo (isitshixo esisisiseko).
Yithini na le mithetho xa ucinga ngokuklanywa kwe-database? Enyanisweni kulula.
1. Kucima ukuphindaphinda
Umgaqo wokuqala ubeka ukuba akufanele senze idatha ngokuphindaphindiweyo kumqolo omnye wetafile. Kwindawo yoluntu yolwazi, le ngcamango ibhekiswe njenge-atomicity table. Iidable ezihambelana nalo mgaqo zithi i-athomu. Makhe sihlolisise lo mgaqo ngomzekelo weklasi: itafile ngaphakathi kwedatha yolwazi lwabantu olugcina ulwalamano-ophantsi. Ngeenjongo zomzekelo wethu, siya kubeka umgaqo wo shishino ukuba umphathi ngamnye unokuba nomnye okanye abangaphantsi kweso sithuba xa omnye phantsi angenakho umphathi omnye.
Intuitively, xa udala uluhlu okanye ispredishithi ukulandelela le ngcaciso, sinokudala itafile ngala masimi alandelayo:
- UMphathi
- Ngaphantsi1
- Ngaphantsi2
- Ngaphantsi.3
- Ngaphantsi4
Nangona kunjalo, khumbula umthetho wokuqala owenziwe ngu-1NF: Ukuphelisa iikholomu eziphindaphindiweyo kwitafile enye. Ngokucacileyo, iCandelo eliPhantsi1-eliphantsi 4 liphindaphinda. Thatha isikhashana uze ucamngce ngeengxaki eziphakanyiswe ngolu hlobo. Ukuba umphathi unomnye ongaphantsi, iikholeji eziphantsi kwe -2 ziphantsi nje zigcinwe kwindawo yokugcina (into exabisekileyo yexabiso ledatha). Ukongezelela, cinga imeko apho umphathi sele ephethe abaphantsi 4 - kwenzeka ntoni ukuba uthatha omnye umqeshwa? Isakhiwo seseta sonke sidinga ukulungiswa.
Kule ngongoma, ingcamango yesibini eqaqambileyo ivela kwii-novice ze-database: Asifuni ukuba nekholomu enye kwaye sifuna ukuvumela inani elitshintshayo lokugcina idatha. Masizame into enje:
- UMphathi
- Abaphantsi
Kwaye insimu ephantsi iqulethe ukungena ezininzi kwifomu ethi "Mary, Bill, Joe."
Esi sisombululo sisondele, kodwa singaphantsi kweempawu. Ikholamu engaphantsi iseyi-duplicative ne-non-atomic. Yintoni eyenzekayo xa sifuna ukungongeza okanye ukususa ophantsi? Kufuneka sifunde kwaye sibhale yonke into ekhoyo etafileni. Oku akuyona into ebalulekileyo kule meko, kodwa kuthekani ukuba umphathi omnye unabasebenzi abayikhulu? Kwakhona, luyinkimbinkqubo yokukhetha idatha esuka kwi database kwimibandela ezayo.
Nayi ithebula eyanelisa umgaqo wokuqala we-1NF:
- UMphathi
- Ngaphantsi
Kule meko, ngamnye ongaphantsi unokungena omnye, kodwa abaphathi banakho ukungena.
2. Ukuchonga iSisiseko esiPrayimari
Ngoku, uthini ngomgaqo wesibini: khetha umqolo ngamnye ngekholam ekhethekileyo okanye isethi yamakholomu (eyona nto iphambili )? Unokujonga ngetafile ngasentla kwaye ucetyise ukusetyenziswa kwekholam ephantsi njengeyona nto ephambili. Enyanisweni, ikholomu elingaphantsi ngumviwa ochanekileyo kwinqanaba elisisiseko ngenxa yokuba imithetho yethu yezoshishino ichazwe ukuba ngamnye ongaphantsi unokuba nomphathi omnye kuphela. Nangona kunjalo, idatha esiyikhethileyo ukuyigcina etafileni yethu yenza ukuba isisombululo esingaphantsi. Kwenzeka ntoni ukuba siqeshe omnye umsebenzi ogama linguJim? Sinokugcina njani ulwalamano lwakhe nomphathi-phantsi kwi database?
Kungcono ukusebenzisa i-identifier ekhethekileyo (njenge-ID yomqeshwa) njengeyona nto ephambili . Itafile yethu yokugqibela ibonakala ngathi:
- I-ID yomphathi
- I-ID ephantsi
Ngoku, itafile yethu ifom eqhelekileyo yokuqala! Ukuba ungathanda ukuqhubeka nokufunda malunga nokuqhelekileyo, funda amanye amanqaku kulolu chungechunge: