Kuyika Chidziwitso mu Fomu Yachiwiri Yachizolowezi
Pa mwezi watha, tawona mbali zingapo za normalizing table table. Choyamba, tinakambirana mfundo zoyambirira za database. Nthawi yotsiriza, tafufuza zofunika zomwe zinayikidwa ndi fomu yoyamba (1NF). Tsopano, tiyeni tipitirize ulendo wathu ndikutsegula mfundo zachiwiri chachiwiri (2NF).
Kumbukirani zofunikira zonse za 2NF:
- Chotsani magwero a deta omwe amagwiritsidwa ntchito pa mizere yambiri ya tebulo ndikuyika iwo mu matebulo osiyana.
- Pangani maubwenzi pakati pa matebulo atsopanowu ndi oyambirira awo pogwiritsa ntchito makiyi akunja.
Malamulowa akhoza kufotokozedwa mwachidule: 2NF amayesa kuchepetsa kuchuluka kwa deta patebulo powulanda, kuyika mu tebulo latsopano ndikupanga mgwirizano pakati pa matebulo.
Tiyeni tione chitsanzo. Tangoganizani sitolo ya pa Intaneti yomwe imapereka mauthenga okhudzana ndi makasitomala. Angakhale ndi tebulo limodzi lotchedwa Amtundu ndi zinthu zotsatirazi:
- CustNum
- Dzina loyamba
- Dzina lomaliza
- Adilesi
- Mzinda
- State
- ZIPu
Kuwoneka mwachidule pa tebulo ili kumawulula zazing'ono zowonjezera deta. Tikusunga "Sea Cliff, NY 11579" ndi "Miami, FL 33157" zolembedwamo kawiri. Tsopano, izo sizikhoza kuwoneka ngati zochuluka-zowonjezera yosungirako mu chitsanzo chathu chophweka, koma talingalirani malo osokonekera ngati ife tiri ndi mizere zikwi mu tebulo lathu. Kuonjezera apo, ngati code ya ZIP ya Sea Cliff ikasintha, tidzasintha kusintha m'malo ambiri m'mabuku.
Mu 2NF-zomangamanga zomangamanga zowonjezera, uthenga wodalirikawu umachotsedwa ndikusungidwa pa tebulo lapadera. Gome lathu latsopano (tiyeni tiyitane ZIPs) lingakhale ndizinthu zotsatirazi:
- ZIPu
- Mzinda
- State
Ngati tikufuna kukhala opambana kwambiri, tikhoza kudzaza tebulo izi pasadakhale - positi ofesi imapereka mayina a zizindikiro zonse za ZIP ndi maubwenzi awo a mzinda / dziko. Ndithudi, mwakumanapo ndi vuto limene deta yamtundu uwu inagwiritsidwa ntchito. Wina amene akulemba angakhale akufunsani inu code yanu yapamwamba choyamba ndikudziŵa mzinda ndi boma lomwe mukuyitana. Makonzedwe oterewa amachepetsa zolakwika za opareshoni ndikuwonjezereka bwino.
Tsopano popeza tachotsa deta yowonjezera kuchokera pa tebulo la Customers, takhutitsa lamulo loyamba la mawonekedwe achiwiri. Tifunika kugwiritsa ntchito makiyi akunja kuti mutumikire matebulo awiri pamodzi. Tidzagwiritsa ntchito foni ya ZIP (chinsinsi chachikulu kuchokera pa tebulo la ZIPs) kuti tipeze ubale umenewo. Pano pali magulu atsopano a Olemba:
- CustNum
- Dzina loyamba
- Dzina lomaliza
- Adilesi
- ZIPu
Tsopano tachepetsa kuchuluka kwa chidziwitso chokwanira chomwe chatsopanocho chikugwiritsidwa ntchito ndipo mawonekedwe athu ali muwonekedwe yachiwiri!
Ngati mukufuna kuonetsetsa kuti deta yanu ndi yachibadwa, fufuzani nkhani zina zowonjezera:
- Maziko Okhazikika Okhazikika
- Kuyika Fomu Yanu Yogulitsa mu Fomu Yoyamba Yodziwika
- Kuyika Zotsatira Zanu mu Fomu Yachiwiri Yachizolowezi
- Kuyika Fomu Yanu ya Chitukuko mu Fomu Yachiwiri Yachikhalidwe