Idatha yoBudlelwane

Ulwalamano lwentlupheko luyi-backbone yazo zonke iinkcukacha zolwazi

Ulwalamano lusekwa phakathi kwetafile ezimbini zeenkcukacha zee- tafile xa itheyibhile enye ineqhosha langaphandle elibhekiselele kwisitshixo esisisiseko senye itafile. Le ngongoma engundoqo kwisiseko sedatha yobudlelwane.

Indlela Eyona Ngundoqo Yemvelaphi Esebenzayo Ukuseka Ubudlelwane

Makhe sihlolisise iisiseko zezicwangciso zaseprayimari nakwamanye amazwe. Iprayimari ebalulekileyo ichonga i rekodi nganye etafileni. Luhlobo lomfaki- mbuzo oqhelekileyo oqhelekileyo kwikholam yokuqala etafileni kwaye unokuveliswa ngokuzenzekelayo ngedatha ukuqinisekisa ukuba iyingqayizivele.

Ikhonkco langaphandle linye iqhosha lomviwa (ingeyona nto ephambili) esetyenziselwa ukudibanisa irekhodi kwedatha kwelinye itafile.

Ngokomzekelo, khawucinge ngala macwecwe amabini achonga ukuba utitshala ufundisa yiphi ikhosi.

Apha, ikona ephambili yetafile yeCandelo le-Course_ID. Isihluthulelo sawo sangaphandle nguMfundisi_ID:

Uyabona ukuba ikhiye wangaphandle kwiiKhosi zidibanisa ukhiye ophambili kwiTitshala:

Singaxelela ukuba u-Teacher_ID ukhiye wangaphandle uthe wanceda ukuseka ubudlelwane phakathi kweeKhosi kunye neetafile zootitshala.

Iintlobo zoLwazi loLwazi

Ukusebenzisa izitshixo zangaphandle, okanye ezinye izitshixo zomviwa, unokuphumeza iintlobo ezintathu zobudlelwane phakathi kweetafile:

Ngamnye-omnye : Olu hlobo lolwalamano luvumela irekodi enye kuphela kwicala ngalinye lolwalamano.

Isisiseko esisisiseko sibhekiselele kwiirekhodi enye - okanye akukho - kwelinye itafile. Umzekelo, emtshatweni, ngamnye umlingane unomnye umlingane omnye. Olu hlobo lolwalamano lunokusetyenziswa kwitafile enye kwaye ngoko alisebenzisi ukhiye wangaphandle.

Unye ukuya kubaninzi : Ulwalamano olulodwa ukuya kwamanye luvumela irekhodi elilodwa kwitheyibhile enye ukuba linxulumane neerekodi ezininzi kwenye ietafile.

Cinga ishishini kunye neenkcukacha ezineenkcukacha zabathengi kunye nee-Orders tables.

Umthengi omnye unokuthenga amagosa amaninzi, kodwa umyalelo omnye awukwazi ukudibaniswa nabaxhasi abaninzi. Ngako oko iTheyibhile yokuLawula iya kuba nekona yangaphandle ehambelana neyona nto ephambili yetafile yabathengi, ngelixa iithebula zabathengi bengenanto yokwamanye amazwe ekhomba kwiTheyard Orders.

Uninzi kuninzi : Olu luhlobo oluyinkimbinkimbi apho iingxelo ezininzi etafileni zinokudibanisa neerekhodi ezininzi kwelinye itafile. Ngokomzekelo, ishishini lethu lingafuneki kuphela kubaThengi kunye neeDrafti zeeMyalelo, kodwa mhlawumbi lifuna iThebula leMveliso.

Kwakhona, ubudlelwane phakathi kwabathengi kunye ne-Orders table yinto enye, kodwa qwa lasela ubudlelwane phakathi kwee-Orders kunye neMikhiqizo yetafile. Umyalelo unokudibanisa iimveliso ezininzi, kwaye umkhiqizo unokudibaniswa nemiyalelo emininzi: abathengi abaningana bangenisa umyalelo oqulethe ezinye iimveliso ezifanayo. Olu hlobo lolwalamano ludinga ubuncinane kwiibhile ezintathu.

Ziziphi iiDatabase zoBudlelwane obubalulekileyo?

Ukuseka ubudlelwane obumanyeneyo phakathi kweethala zeenkcukacha zedatha kunceda ukuqinisekiswa kwengqibelelo yolwazi, ukufaka isandla kwi-database. Ngokomzekelo, kuthini ukuba asizange sidibanise naziphi na iitheyibhile ngokusebenzisa ukhiye wangaphandle kwaye kunoko nje ukudibanisa idatha kwiingqungquthela zeeKhosi kunye noTitshala, njengaye:

Olu luyilo luyi-inflexible kwaye luphulaphula umgaqo wokuqala wokuqulunqwa kwedatha, Ifom yokuqala yesiQhelo (1NF), echaza ukuba iteksi nganye nganye kufuneka iqulethe idatha enye, ecacileyo yedatha.

Okanye mhlawumbi siye sagqiba kwekwengeza irekhodi yesibini yeKarmen, ukwenzela ukuba siqinisekise i-1NF:

Oku kusekwakhiwa okubuthathaka, ukuzisa ukuphindaphinda okungadingekile kunye nento ebizwa ngokuba yi- anomalies yokufaka idatha , oko kuthetha ukuba inokufaka isandla kwidibaniselwano ezingahambelaniyo.

Ngokomzekelo, ukuba utitshala unamarekhodi amaninzi, kuthekani ukuba idatha ethile idinga ukulungiswa, kodwa umntu owenza ukuhlela idatha akaqondi ukuba iirekhodi ezininzi zikhona? Itafile zaza kuba neenkcukacha ezahlukeneyo zomntu ofanayo, ngaphandle kwendlela ecacileyo yokuyijonga okanye ukuyiphepha.

Ukuphula le tafile kwiibhuleta ezimbini, ootitshala kunye neekhosi (njengoko ziboniswe ngasentla), zidala ubudlelwane obufanelekileyo phakathi kwedatha kwaye ngoko kunceda ukuqinisekiswa kweenkcukacha kunye nokuchaneka.