Igama elivamile elisetshenziselwa ukuklanywa kwedatha "i-database ehlobene" -kodwa ubudlelwane be-database akuyona into efanayo futhi akusho, njengoba igama layo libonisa, ubuhlobo phakathi kwamatafula. Kunalokho, ubudlelwane be-database buvele bubhekisele etafuleni elilodwa kwisitatimende sokuxhumana.
Esikhathini sedatha ehlobene , ithebula lihlobene ngoba ligcina ubudlelwane phakathi kwedatha efomini yayo emgqeni. Amakholomu ayimfanelo yetafula, kanti imigqa ibonisa amarekhodi wedatha. Umugqa owodwa uyaziwa njengabaqambi be-tuple kuya kumadaski.
Incazelo kanye nezindawo zohlobo
Ubuhlobo, noma itafula, ku-database yokuxhumana kunezindawo ezithile. Okokuqala, igama layo kumele lihlukile kwi-database, okungukuthi i-database ayikwazi ukuqukatha amathebula amaningi wegama elifanayo. Okulandelayo, ubudlelwane ngamunye kumele babe neqoqo lamakholomu, noma izimfanelo, futhi kufanele kube neqoqo lemigqa yokuqukatha idatha. Njengamagama etafula, akukho zimfanelo ezingaba negama elifanayo.
Okulandelayo, akukho tuple (noma umugqa) kungaba impinda. Ngokwenzayo, i-database ingase iqukathe imigqa ephindwe kabili, kodwa kufanele kube nemikhuba ekhona yokugwema lokhu, njengokusetshenziswa kwezihluthulelo eziyisisekelo ezihlukile (okulandelayo).
Njengoba kunikezwe ukuthi i-tuple ayikwazi ukuphindaphindiwe, kulandela ukuthi ubudlelwane kufanele buqukathe okungenani umklamo owodwa (noma ikholomu) okhomba i-tuple ngayinye (noma umugqa) ngokukhethekile. Lokhu ngokuvamile kuyisihluthulelo esiyinhloko. Leli khiye eliyinhloko alikwazi ukuphinda liphindwe. Lokhu kusho ukuthi akukho tuple engaba nayo efanayo, ukhiye oyinhloko. Isihluthulelo asinaso inani le- NULL , elisho nje ukuthi inani kufanele liyaziwa.
Ngaphezu kwalokho, iseli ngalinye, noma insimu, kufanele libe nenani elilodwa. Isibonelo, awukwazi ukungena into efana no "Tom Smith" futhi ulindele ukuthi i-database iqonde ukuthi unalo igama lokuqala nelokugcina; Kunalokho, i-database izoqonda ukuthi inani lensiza yilokho okufakiwe.
Okokugcina, zonke izimfanelo-noma izinsika-kumele zibe yindawo efanayo, okusho ukuthi kumele babe nohlobo olufanayo lwedatha. Awukwazi ukuxuba uchungechunge nenombolo esitokisini esisodwa.
Zonke lezi zakhiwo, noma izinkinga, ziqinisekisa ukuthembeka kwedatha, kubalulekile ukulondoloza ukunemba kwedatha.