AKUNYE NULL Imithintelo kwi-Microsoft SQL Server

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:

Kukho konke ukudala izithintelo ze-NULL kwi-Microsoft SQL Server!