Funda into eyenza ukhiye olungundoqo okanye olungundoqo kwisiseko sedatha
Iyiphi ikona ephambili? Kwihlabathi leenkcukacha , inqakrazo ephambili yetafile ehlobeneyo ichaza kuphela irekhodi ngalinye kwitafile. Iinkcukacha zolwazi zisebenzisa izitshixo zokuthelekisa, ukuhlela, nokugcina iirekhodi, kunye nokudala ubudlelwane phakathi kwamarekhodi.
Ukukhetha ikona ephambili kwisiseko sedatha yenye yezona nyathelo ezibalulekileyo kwinkqubo. Ingaba ngumxholo oqhelekileyo oqinisekileyo ukuba uyingqayizivele njengeNombolo yoKhuseleko lweNtlalo etafileni engenakho irekhodi enye ngomntu ngamnye okanye - ngokukhethekileyo - inokuveliswa yinkqubo yolawulo lweenkcukacha njenge-identifier, okanye i-GUID , kwi- Microsoft SQL Server . Izitshixo zaseprayimari zinokuthi zibandakanye impawu enye okanye iimpawu ezininzi ngokudibeneyo.
Izitshixo zaseprayimari ziqhagamshelo ezizodwa kwiinkcukacha ezihambelanayo nakwezinye iitheyibhile apho isisiseko esisisiseko sisetyenziswa. Kumele ifakwe xa irekhodi lenziwe, kwaye akufanele liguqulwe. Itafile nganye kwiziko ledatha inekholomu okanye amabini ngokukodwa ngokuphambili.
Umzekelo oyintloko
Cinga ukuba unetafile yeZIFUNDO eziqulethe irekodi yomfundi ngamnye kwiyunivesithi. Inombolo ye-ID yomfundi oyingqayizivele yinto efanelekileyo yokhetho oluphambili kwitheyibhile labafundi. Igama lokuqala nelokugqibela lomfundi alikho ukhetho olufanelekileyo kuba kukho ithuba lokuba abafundi abangaphezu kwesinye babe nokuba negama elifanayo.
Olunye ukhetho olubi lwezixhobo eziphambili ziquka ikhowudi ye-ZIP, idilesi ye-imeyile kunye nomqeshi, zonke ezo zingatshintsha okanye zimelele abantu abaninzi. Isihlomelo esisetyenzisiweyo njengesisiseko esisisiseko kufuneka sibe sisodwa. Nokuba iinombolo zoKhuseleko lweNtlalo ziyakutshintsha xa ulawulo loKhuselo loLuntu lubuyisela inamba kumntu ochaphazelekayo ngobusela bezazisi. Abanye abantu abanayo inombolo yeNtlalo yoKhuseleko. Nangona kunjalo, kuba zombini loo matyala ayinqabile. Izinombolo zoKhuseleko lweNtlalo zinokuzikhethela ukhetho oluphambili.
Iingcebiso zokukhetha iiKeyona eziPrayimari ezilungileyo
Xa ukhetha i-key eyona nto ibalulekileyo, i-database lookups ihamba ngokukhawuleza kwaye inokwethenjelwa. Khawukhumbule nje:
- Gcina lifutshane . Ngenxa yokuba isisiseko esisisiseko sisetyenziselwa ukujonga kunye nokuthelekisa, isisiseko esisisiseko esincinci sithetha ukuba inkqubo yolawulo lweenkcukacha iyakwenza inkqubo ngokukhawuleza kunokuba yinto ephambili eyona nto.
- Sebenzisa inombolo kwinqakrazo ephambili xa kunokwenzeka. I-SQL Server okanye ezinye iinkqubo zokulawula iinkcukacha iinkqubo zedata yeenkcukacha ngokukhawuleza kuneentlobo zeenkcukacha zedatha.
- Gcina kulula. Ungasebenzisi naziphi na iimpawu ezikhethekileyo, izithuba ezifakiwe, okanye umxube wexabiso eliphezulu kunye nezantsi.
- Ungalokothi utshintshe isitshixo esisisiseko emva kokuba usibekele.