Fomu yachitatu (3NF) ndi ndondomeko yachinsinsi yomwe imathandizira kukhulupirika kwa deta pomanga mfundo zapamwamba zomwe zimaperekedwa ndi Fomu Yoyamba (1NF) ndi Fomu Yachiwiri Yachiwiri (2NF).
Zofunika Zamaonekedwe Achitatu
Pali zofunika ziwiri zoyenera kuti deta ikhale ya mawonekedwe apamwamba:
- Mzerewu uyenera kukwaniritsa zofunikira za 1NF ndi 2NF .
- Mazenera onse a deta ayenera kudalira makiyi apamwamba , kutanthauza kuti mtengo uliwonse wa m'khola ungachoke ku chinsinsi chokha.
Ponena za Chikhazikitso Chofunikira Chachikulu
Tiyeni tipitirize kufufuza zomwe tikutanthawuza podziwa kuti mizati yonse iyenera kudalira pachinsinsi chachikulu.
Ngati mtengo wa m'khola ungachoke ku chinsinsi choyamba ndi mzere wina patebulo, umaphwanya 3NF. Ganizirani ndondomeko ya ogwira ntchito ndi ndondomeko izi:
- Wogwira ntchito
- Dzina loyamba
- Dzina lomaliza
Kodi maina awiri onse ndi dzina loyamba amadalira pa mtengo wa EmployeeID? Chabwino, kodi LastName ikhoza kudalira Dzina Loyamba? Ayi, chifukwa palibe chomwe chimachitika mu LastName chingasonyeze kufunika kwa FirstName. Kodi Dzina Loyamba Lingagonjetse Dzina Lina? Ayi, chifukwa chimodzimodzi ndizoona: kaya Dzina Lina likhoza kukhala lotani, silikanakhoza kupereka ndondomeko ya kufunika kwa Dzina Loyamba. Choncho, tebulo ili ndi 3NF yovomerezeka.
Koma ganizirani Magalimoto awa patebulo:
- Magalimoto
- Wopanga
- Chitsanzo
Wopanga ndi chitsanzo akhoza kutenga kuchokera ku VehicleID - koma Chitsanzo chingathenso kuchoka kwa Wopanga chifukwa choyimira galimoto chimangopangidwa ndi wopanga winawake. Mapangidwe a tebulo awa si ovomerezeka a 3NF, ndipo akhoza, chifukwa chake, kumabweretsa zolakwika za data. Mwachitsanzo, mungasinthire wopanga popanda kusinthira chitsanzocho, poyambitsa zolakwika.
Kuti timvetsetse, tifunika kusuntha mbali yowonjezera yowonjezera ku tebulo lina ndikutanthauzira pogwiritsa ntchito makiyi akunja. Izi zingapangitse magome awiri:
Magalimoto Zamagetsi
Mu tebulo ili m'munsimu, ModelID ndi fungulo yachilendo ku tebulo lachitsanzo:
- Magalimoto
- Wopanga
- ModelID
Mapepala a Zithunzi
Gome latsopanoli limapanga mafano osiyanasiyana kwa opanga. Ngati mukufuna kusintha mauthenga amtundu uliwonse wa galimoto, mungachite izi patebulo lino, osati mu gome lamagalimoto.
- ModelID
- Wopanga
- Chitsanzo
Masamba Owonetsedwa mu 3NF Model
Tebulo ikhoza kukhala ndi gawo lochokera - limodzi lowerengedwa molingana ndi zigawo zina patebulo. Mwachitsanzo, taganizirani tebulo ili la malamulo a widget:
- Nambala yogulira
- Nambala ya Nambala
- Mtengo wagawo
- Chiwerengero
- Chiwerengero
Zosintha zonse 3NF zotsatila chifukwa zingatengedwe ndi kuchulukitsa mtengo wogula ndi kuchuluka, osati kukhala wodalirika pa chofunikira chachikulu. Tiyenera kuchotsa pa tebulo kuti tizitsatira fomu yachiwiri.
Ndipotu, popeza izo zachokera, ndi bwino kusunga izo mu deta konse.
Titha kungowerengera "phokoso" pamene mukufufuza mafunso. Mwachitsanzo, mwina tinagwiritsa ntchito funso ili kale kuti tipeze nambala ya mayendedwe ndi totali:
SANKANI Ndalama Yowonjezera, Total FROM WidgetOrdersTitha kugwiritsa ntchito funso ili:
Sankhani Order Order, UnitPrice * Quantity AS Total FROM WidgetOrderskuti akwaniritse zotsatira zomwezo popanda kuphwanya malamulo ovomerezeka.