Iingenelo zokusebenzisa imiqobo engapheliyo
Ngokudala i-contraceptive UNIQUE, abalawuli be-SQL Server bachaza ukuba ikholomu inokuthi ingenayo ixabiso elincinci. Xa udala inqununu entsha YONYAKA, i-SQL Server ihlola ikholam ekuthethwa ngayo ukuba iqinisekise ukuba iqukethe nayiphi na imilinganiselo yee-duplicate. Ukuba itheyibhile iqukethe izihlandlo ezikhoyo ngaphambili, umyalelo wokudala imithintelo uyaphela. Ngokufanayo, xa unomqobo ongekho phantsi kwikholam, uzama ukufaka okanye ukuguqula idatha ebangela ukuba iziphindaphindwa zibekho nazo zihluleka.
Kutheni uSebenzise iziNxakatho ezingekho
ISINQUBO esingenasisiseko kunye nesisiseko esisisiseko sokunyanzelisa ukuzodwa, kodwa kukho amaxesha apho inkcenkcesho engeyiyo yinto engcono.
- Sebenzisa umqobo ongapheliyo xa ufuna iimithintelo ezininzi kwitafile. Unokuqhagamshela kuphela isitshixo esisisiseko kwitafile.
- Sebenzisa umqobo ongapheliyo xa ikholomu ivumela iimpawu ezingekho phantsi. Izithintelo eziphambili zeprayimenti zingaxhomekeka kuphela kwiikholomu ezingavumeli amanani angenanto.
Ukudala isiXhosa esingunaphakade
Kukho iindlela ezininzi onokwenza umqobo ongekho phantsi kweSQL Server. Ukuba ufuna ukusebenzisa iTransact-SQL ukuze ungeze impazamo engekho emthethweni kwitafile ekhoyo, ungasebenzisa isitatimende se-ALTER TABLE, njengoko kuboniswe ngezantsi:
I-ALTER ITHEBHALA YENZA I-CONSTRAINT UNIQUE ()Ukuba ukhetha ukusebenzisana ne-SQL Server usebenzisa izixhobo ze-GUI, unokwenza kwakhona umqobo ongekho UNIQUE usebenzisa i- SQL Server Management Studio . Nantsi indlela:
- Vula i-SQL Server Management Studio .
- Ukwandisa ifowuni ifolda yedatha apho ufuna ukudala imithintelo.
- Cofa iqhosha kwitafile apho ufuna ukufaka umqobo kunye nokucofa uMilo .
- Kwimenyu yeDesign Design , qhafaza ii-Indexes / Keys .
- Kwibhokisi yencoko yababhali / iiKhentshi, nqakraza Yongeza .
- Khetha ukhiye oyingqayizivele kwiluhlu lokuhlahla uhlobo .
IZINQUBO ZEMINYANGO NGEZI-Index ze-UNIQUE
Kukho ukudideka malunga nomda phakathi kwe-UNIQUE constraint kunye ne-UNIQUE index. Ngethuba ungasebenzisa imiyalelo eyahlukeneyo yeTransact-SQL ukuyidala (ALTER TABLE ... YENZISA i-CONSTRAINT kwiimimiselo uze udale i-INDEX INDEX yeefayili), inemiphumo efanayo, inxalenye enkulu. Enyanisweni, xa udala i-contraceptive UNIQUE, ngokuqinisekileyo yenza i-INIQUE index kwi tafile. Kubalulekile ukuqaphela, nangona kunjalo, ukuba kukho ukungafani:
- Xa udala isalathisi, unokongeza iinketho ezongezelelweyo kumyalelo wokudala.
- Ikholamu ephantsi kwenkqunqo engavumelekanga ingasetyenziswa njengokhiye wangaphandle .