Video: Tsis yog NULL hauv VBScript?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Lus ceeb toom: VBScript IsNull Function
IsNull rov muaj tseeb yog hais tias yog Null ; uas yog, nws muaj tsis muaj cov ntaub ntawv siv tau; txwv tsis pub, IsNull rov False. Cov Null tus nqi qhia tias qhov sib txawv muaj tsis muaj cov ntaub ntawv siv tau. Null tsis yog tib yam li Empty, uas qhia tias muaj qhov sib txawv tsis yog tseem tau pib.
Yog li ntawd, iS NULL yog khoob?
Null txhais tsis muaj dab tsi. Nws tsuas yog qhov tseeb xwb. Null yog tus nqi ntawm kev siv sib txawv. Npua hlua is a dawb paug tus nqi, txhais tau tias txoj hlua tsis muaj dab tsi.
iS NULL muaj nuj nqi hauv JavaScript? Cov JavaScript hom qub null sawv cev rau qhov tsis txhob txwm ua ntawm tus nqi - nws feem ntau yog teem rau lub hom phiaj los qhia tias qhov sib txawv tau raug tshaj tawm tab sis tseem tsis tau muab cov nqi. Qhov no sib piv null los ntawm qhov zoo sib xws tus nqi qub undefined, uas yog ib qho tsis txhob txwm tsis muaj ib qho khoom muaj nqis.
Yog li ntawd, ua li cas koj sau tsis sib npaug rau hauv VBScript?
(A == B) yog False. Tshawb xyuas seb tus nqi ntawm ob lub operands puas yog sib npaug los yog tsis yog , yog muaj nuj nqis tsis sib npaug ces qhov xwm txheej yuav muaj tseeb. (A B) yeej muaj tseeb. Xyuas yog tias tus nqi ntawm sab laug operand ntau dua tus nqi ntawm txoj cai operand, yog tias muaj ces qhov xwm txheej yuav tshwm sim.
Koj siv null li cas hauv JavaScript?
' Null' hauv JavaScript ' Null ' yog lo lus tseem ceeb hauv JavaScript uas txhais tau hais tias 'tsis muaj nqi' lossis tsis muaj qhov muaj nqis. Yog tias koj xav rho tawm qhov sib txawv ntawm nws cov nqi, koj tuaj yeem muab ' null ' rau nws. Dhau li ntawm qhov no, zoo li lwm yam khoom, nws yeej tsis raug xa mus rau qhov sib txawv los ntawm JavaScript.
Pom zoo:
Tsis yog NULL hauv kev nkag?
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Tsis yog NULL txhais li cas hauv SQL?
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Dab tsi yog null thiab tsis null hauv SQL?
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