Ukulungiswa kweDatabase yakho
Ukuba usebenze kunye nolwazi lwexeshana, ithuba lokuba uvile ixesha eliqhelekileyo. Mhlawumbi umntu ucele kuwe "Ngaba le nkcukacha ziqhelekileyo?" okanye "Ngaba oko ku BCNF ?" Ukuqheleka ngokuqhelekileyo kuhlanjululwe eceleni njengento yokunethezeka eyaziwa kubafundi kuphela. Nangona kunjalo, ukwazi imigaqo yokuqhelanisa nokuyibeka kwimisebenzi yakho yesikhokelo kwidatha yakho yonke imihla akuyiyo yonke into enzima kwaye inokuphucula kakhulu ukusebenza kwe-DBMS yakho.
Kule nqaku, siza kuzisa ingcamango yesiqhelo kwaye sijonge ngokufutshane iifom eziqhelekileyo eziqhelekileyo.
Yintoni i-Normalization?
Ukumisela inkqubo yinkqubo yokuhlela ngokufanelekileyo idatha kwiziko ledatha. Kukho iinjongo ezimbini zeenkqubo eziqhelekileyo: ukucima idatha engapheliyo (umzekelo, ukugcina idatha efanayo kunye netafile enye) nokuqinisekisa ukuxhomekeka kwedatha kunengqiqo (kuphela ukugcina idatha edibeneyo etafileni). Zomibini zezi ziinjongo ezifanelekileyo njengoko zinciphisa inani leendawo idata lidliwayo kwaye liqinisekise ukuba idatha igcinwe ngokufanelekileyo.
Iifom eziqhelekileyo
Uluntu wolwazi luye lwaphuhlisa uluhlu lwezikhokelo zokuqinisekisa ukuba iinkcukacha zolwazi ziqhelekileyo. Ezi zibizwa ngokuba njengeziqhelo eziqhelekileyo kwaye zibalwa ukusuka kwelinye (ifom ephantsi kunazo zonke, ngokubhekiselwe kwifomu eqhelekileyo okanye 1NF) ukuya kweyesihlanu (yesihlanu ifom yesiqhelo okanye 5NF). Kwizicelo eziphathekayo, uya kufumana i-1NF, 2NF, ne-3NF kunye ne-4NF ngezihlandlo. Ifom yesibini yesiqhelo ayibonakali kakhulu kwaye ayiyi kuxutyushwa kule nqaku.
Ngaphambi kokuba siqale ingxoxo yethu yeefom zesiqhelo, kubalulekile ukubonisa ukuba zikhokelo nezikhokelo kuphela. Ngamanye amaxesha, kubalulekile ukuba ulahleke kubo ukuhlangabezana neemfuno zoshishino. Nangona kunjalo, xa uguquko lwenzeka, kubaluleke kakhulu ukuvavanya nayiphi na imilinganiselo enokuthi ibe nayo kwinkqubo yakho kunye neakhawunti ngokungahambelani. Oko kwathiwa, makhe sihlolisise iifom eziqhelekileyo.
Ifom yokuQala eqhelekileyo (1NF)
Ifom yokuqala eqhelekileyo (1NF) isetyenziselwa imigaqo esemiselweyo yedatha ehleliweyo:
- Ukuphelisa iikholomu zokuphinda kwitafile enye.
- Yenza amacwecwe ahlukeneyo kwiqela ngalinye leenkcukacha ezihambelanayo kwaye uchaze umqolo ngamnye ngekholam ekhethekileyo okanye isethi yamakholomu (eyona nto iphambili ).
Ifomu yesiBini yesiQhelo (2NF)
Ifom yesiqhelo yesiqhelo (2NF) idibanisa ngakumbi umgaqo wokususa idatha ephindaphindiweyo :
- Ukudibanisa yonke imfuno yefomu yokuqala evamile.
- Susa iifomfayile zedatha ezisebenzayo kwimigca emininzi yetafile uze uzibeke kwietafile ezihlukeneyo.
- Yakha ubudlelwane phakathi kwezi tafile ezitsha kunye nabaphambili babo ngokusebenzisa ukusetyenziswa kwamanye amazwe .
Ifomu yesithathu eqhelekileyo (3NF)
Ifom yesithathu eqhelekileyo (3NF) iya kuhamba enye inkulu enkulu:
- Ukudibanisa yonke imfuno yesibini ifom yesiqhelo.
- Susa iikholomu ezingaxhomekeke kwi-key key.
Ifom yeB Boyce-Codd eqhelekileyo (BCNF okanye 3.5NF)
Ifom ye-Boyce-Codd eqhelekileyo, ebizwa ngokuba "ifom yesiqhelo sesithathu nesigxina (3.5)", yongeza enye imfuneko:
- Ukudibanisa zonke iimfuno zefomu yesithathu evamile.
- Wonke ummiselo kufuneka ube ngumphambili wokuba ngumviwa.
Ifom yesine ejwayelekile (4NF)
Ekugqibeleni, ifom yesiqhelo sesine (4NF) sinemfuneko eyongezelelweyo:
- Ukudibanisa zonke iimfuno zefomu yesithathu evamile.
- Ulwalamano lukwa-4NF ukuba alukho ukuxhomekeka kwamanani amaninzi .
Khumbula, ezi zikhokelo ziqhelekile. Ukuze idesitenti ibe kwi-2NF, kufuneka kuqala izalise yonke imigaqo ye-1NF yolwazi.
Ngaba ndifanele ndiyiqhele?
Nangona i-normalization database isoloko ingumzekelo omuhle, akusiyo imfuno ebalulekileyo. Enyanisweni, kukho ezinye iimeko apho ukuphulaphula ngamabomu imigaqo yokuqhelaniswa yinto efanelekileyo. Ukufumana oku ngakumbi kwesi sihloko, sifunde Ngaba Ndifanele ndiyiNcedise i-Database My Database?
Ukuba ungathanda ukuqinisekisa ukuba i-database yakho iqhelekileyo, qalisa ngokufunda indlela yokubeka ifowuni yakho kwiFom yeSiqhelo esiQala .