Izinzuzo Zokusebenzisa Izithiyo Ezingavunyelwe Ngaphezu Kwezingqinamba Eziyinhloko Eziyinhloko
Ngokudala isimiso esingavumelekile, abaqondisi be-SQL Server bachaza ukuthi ikholomu lingase lingabi namanani aphindaphindiwe. Uma udala umgomo omusha we-UNIQUE, i-SQL Server ihlola ikholomu embuzweni ukuze inqume ukuthi iqukethe noma yiziphi izimali eziphindwe kabili. Uma ithebula liqukethe okuphindaphindiwe okukhona, umyalo wokudala ukuphoqelela uhluleka. Ngokufanayo, uma unenkinga engavumelekile ekholomu, uzama ukwengeza noma ukuguqula idatha engabangela ukuthi izimpinda zibe khona nazo zihluleka.
Kungani Kufanele Usebenzise Izingqinamba UNIQUE
ISIQINISO esingavunyelwe futhi ukhiye oyinhloko kokubili ukuphoqelela okuhlukile, kodwa kunezikhathi ukuthi inkinga engavunyelwe yi-UNIQUE ingcono kakhulu.
- Sebenzisa inkinga engavumelekile uma ufuna izinkinga eziningi etafuleni. Ungabhalela kuphela ukhiye owodwa oyinhloko etafuleni.
- Sebenzisa isibopho esingavunyelwe uma ikholomu evumela amanani angenalutho. Izivimbelo ezisemqoka ezingamaphesenti zingaxhunyaniswa kuphela namakholomu angavumeli amanani angenamkhawulo.
Ukudala isibopho esingavunyelwe
Kunezindlela eziningi ongakha ukucindezeleka okungavunyelwe ku-SQL Server. Uma ufuna ukusebenzisa i-Transact-SQL ukwengeza imithwalo engavumelekile etafuleni ekhona, ungasebenzisa isitatimende se-ALTER TABLE, njengoba kuboniswe ngezansi:
I-ALTER ITHEBULA YENZA INQUBO YOKUQALA ()Uma ukhetha ukusebenzisana ne-SQL Server usebenzisa amathuluzi we-GUI, ungakha futhi isibopho esingavumelekile usebenzisa i- SQL Server Management Studio . Nansi indlela:
- Vula SQL Server Management Studio .
- Nweba ifolda yamathebula wedatha lapho ufuna khona ukudala umgomo.
- Chofoza ngakwesokudla itafula lapho ufuna ukufaka khona ukucindezela bese uchofoza u- Design .
- Emenyu yeDesign Designer, chofoza Izinkomba / Amakhi .
- Ebhokisini lengxoxo ye-Indexes / Keys, chofoza u- Engeza .
- Khetha ukhiye oyingqayizivele ohlwini lohlu lokuhlahlela.
IZINHLANGANO EZINQAKHELEKILE Nama Index Index
Kube khona ukudideka mayelana nokwahlukana phakathi kwesimiso esingavunyelwe kanye no-UNIQUE index. Ngenkathi ungasebenzisa imiyalo ehlukene ye-Transact-SQL ukuyidala (i-ALTER TABLE ... Yengeza i-CONSTRAINT ngezinkinga futhi Yakha INDEX UNIQUE for indexes), inomphumela ofanayo, ingxenye enkulu. Eqinisweni, uma udala isibopho esingavunyelwe, empeleni sakha inkomba engekho emthethweni etafuleni. Kuyaphawuleka ukuqaphela, noma kunjalo, ukuthi kunezinto ezihlukile:
- Uma udala inkomba, ungangezela izinketho ezengeziwe kumyalo wokudala.
- Ikholomu ngaphansi kwesithiyo esingavunyelwe ingasetshenziswa njengesihluthulelo sangaphandle .