Iva nechokwadi chokuti iyo yakawanda yemari yedhadhi yakaiswa
HERE NULL zvinokonzerwa muMicrosoft SQL Server zvinokubvumira kuti utaure kuti korumusi inogona kunge isina zvigaro zveNULL . Paunenge uumba chinyorwa CHISHA cheNULL pane imwe nheyo ye database, SQL Server inotarisa zviri mukati mekhomu zviri mukati maNAL maitiro. Kana iyo chinyorwa ikozvino ine maonero eNULL, zvisikwa zvinopesana zvinokundikana. Kana zvisina kudaro, SQL Server inowedzera iyo HERE NULL zvinodzivirira uye chero ipi zvayo yeramangwana INSERT kana UPDATE mirairo inogona kuita kuti kuve kweNULL kukosha kwekukundikana.
NULL yakasiyana neyero kana zero mutsara wemhando. NULL zvinoreva kuti hapana mukova wakagadzirwa.
Kugadzira kwete NULL Kupindira
Kune nzira dzakawanda iwe unogona kugadzira CHINHU chakashata muSQL Server. Kana uchida kushandisa Transact-SQL kuti uwedzere gwaro reUNIQUE pane tafura iripo, unogona kushandisa izwi re ALTER TABLE, sezvinoratidzwa pasi apa:
ALTER TABLE
ALTER COLUMN HERE NULL
Kana iwe uchida kuyanana neSQL Server uchishandisa GUI zvishandiso, unogonawo kusimbisa kwete NULL zvinodzivirira uchishandisa SQL Server Management Studio. Heino nzira:
- Vhura SQL Server Management Studio.
- Wedzera Tafura yefaira ye database uko iwe unoshuva kugadzira chinetso.
- Kona-pata tafura apo iwe unoda kuwedzera dambudziko uye chengetedza Chigadzirwa.
- Chengetedza ZVA NULL checkbox ye column (s) yaunoda kuti usati WANO NULL zvidzidzo (s).
Izvo zvose zviripo kuumba NOT NULL zvinetso muMicrosoft SQL Server!