Qinisekisa ukuba inani elifanelekileyo leedatha lifakiwe
IMISEBENZI YEZIKHONO kwi-Microsoft SQL Server ikuvumela ukuba ucacise ukuba ikholomu mayingenayo ixabiso le-NULL . Xa udala into entsha ye-NULL engekho kwikholomu yeenkcukacha, iSQL Server ihlola izinto ezikhoyo zamakholomu zazo naziphi na ixabiso le-NULL. Ukuba kukho ikholamu ngoku iqulethe ixabiso le-NULL, indalo yokunyanzelisa iyaphela. Ngaphandle koko, i-SQL Server yongeza i-NULL imithintelo kunye nayiphi na izayo i-INSERT okanye i-UPDATE imilayezo eya kubangela ukuba khona kwexabiso le-NULL liphumelele.
I-NULL ihluke kwi-string okanye ngentambo yesinhlamvu. I-NULL ithetha ukuba akukho nto yokungena eyenziwe.
Ukudala i-NULL Impazamo
Kukho iindlela ezininzi onokwenza umqobo ongekho phantsi kweSQL Server. Ukuba unqwenela ukusebenzisa iTransact-SQL ukuba ungeze isithintelo esingavumelekanga kwitafile ekhoyo, ungasebenzisa isitatimende se-ALTER TABLE, njengoko kuboniswe ngezantsi:
ALTER TABLE
I-ALTER I-COLUMN AKUNYE NULL
Ukuba ukhetha ukusebenzisana ne- SQL Server usebenzisa izixhobo ze-GUI, unokwenza i-contractor NULL ngokungasebenzisi iSQL Server Management Studio. Nantsi indlela:
- Vula i-SQL Server Management Studio.
- Ukwandisa ifowuni ifolda yedatha apho ufuna ukudala imithintelo.
- Cofa iqhosha kwitafile apho unqwenela ukongeza umnqongophinde uze ukhethe Uyilo.
- Hlola i-NOT NULL ibhokisi yokukhangela yekholam (i) apho ufuna ukungahambisani NEMININQUBO NULL.
Kukho konke ukudala izithintelo ze-NULL kwi-Microsoft SQL Server!