2024 Tus sau: Elizabeth Oswald | [email protected]. Kawg hloov kho: 2024-01-13 00:07
Ib tug yuam sij tseem ceeb yog ib tus yuam sij tshwj xeeb. Txhua lub rooj yuav tsum muaj feem ntau ntawm IB lub ntsiab tseem ceeb tab sis nws tuaj yeem muaj ntau tus yuam sij tshwj xeeb. Tus yuam sij tseem ceeb yog siv los txheeb xyuas cov kab lus sib txawv.
Puas yog tus yuam sij tseem ceeb ib txwm muaj?
Tus yuam sij tseem ceeb yog ib txwm muaj nyob hauv txhua SQL. Koj tsis tas yuav qhia meej meej tias nws yog UNIQUE. Ntawm ib sab: Koj tuaj yeem muaj ib tus yuam sij tseem ceeb hauv lub rooj thiab nws yeej tsis tso cai rau qhov muaj nuj nqis.
Tus yuam sij txawv teb chaws tuaj yeem yog null?
By default tsis muaj kev txwv ntawm tus yuam sij txawv teb chaws, tus yuam sij txawv teb chaws tuaj yeem ua tsis tau thiab luam tawm. thaum tsim ib lub rooj / hloov lub rooj, yog hais tias koj ntxiv tej yam kev txwv ntawm uniqueness los yog tsis null ces tsuas yog nws yuav tsis cia lub null / duplicate tus nqi.
Tus piv txwv tseem ceeb yog dab tsi?
Ib tus yuam sij tshwj xeeb yog txheej ntawm ib lossis ntau tshaj ib daim teb / kab ntawm lub rooj uas tshwj xeeb txheeb xyuas cov ntaub ntawv hauv cov ntaub ntawv. Koj tuaj yeem hais tias nws me ntsis zoo li tus yuam sij tseem ceeb tab sis nws tuaj yeem lees txais tsuas yog tus nqi null thiab nws tsis tuaj yeem muaj qhov sib npaug.
Dab tsi yog qhov sib txawv ntawm qhov ntsuas thiab qhov tseem ceeb?
Tus yuam sij tseem ceeb yog qhov tshwj xeeb unique ntsuas. Tsuas yog ib qho tseem ceeb index tuaj yeem txhais tau hauv ib lub rooj. Tus yuam sij tseem ceeb yog siv los txheeb xyuas cov ntaub ntawv tshwj xeeb thiab raug tsim siv lo lus tseem ceeb PRIMARY KEY. Indexs tuaj yeem npog ntau kab ntawv, xws li index zoo li INDEX (columnA, columnB), uas yog qhov sib koom ua ke.
Pom zoo:
Puas yog phagocytes tshwj xeeb lossis tsis tshwj xeeb?
Enzymes pom hauv lub cell ces zom cov kab mob txhawm rau txhawm rau rhuav tshem nws. Raws li phagocytes ua li no rau tag nrho cov kab mob uas lawv ntsib, lawv hu ua tsis tshwj xeeb. Puas yog phagocytes ib feem ntawm cov tshuaj tiv thaiv kab mob tshwj xeeb lossis tsis tshwj xeeb?
Puas yog meristems tshwj xeeb lossis tsis tshwj xeeb?
Meristems yog thaj chaw ntawm cov hlwb tsis tshwj xeeb hauv cov nroj tsuag uas muaj peev xwm faib cov cell. Meristems ua rau cov hlwb tsis tshwj xeeb uas muaj peev xwm dhau los ua ib hom cell tshwj xeeb. Puas yog cov ntaub so ntswg meristematic tshwj xeeb?
Puas yog tshwj xeeb thiab tshwj xeeb?
Raws li lub npe qhov txawv ntawm kev tshwj xeeb thiab kev tshwj xeeb. yog tias kev tshwj xeeb yog thaum tshwj xeeb yog txheej txheem tshwj xeeb. Qhov twg yog Qhov Tshwj Xeeb lossis Tshwj Xeeb? "Specialisation" thiab "
Puas yog lub rooj sib txuas puas muaj tus yuam sij tseem ceeb?
Nyob hauv lub rooj sib txuas, teem lub ntsiab tseem ceeb rausuav nrog tag nrho cov ntsiab lus tseem ceeb ntawm ob lub rooj. … Qhia txog kev sib raug zoo ib-rau-ntau ntawm txhua qhov ntawm ob lub ntsiab lus thiab lub rooj sib txuas. Lub rooj sib txuas yuav tsum nyob ntawm "
Dab tsi yog qhov tseem ceeb thiab vim li cas nws tseem ceeb los txheeb xyuas koj qhov tseem ceeb?
Qhov tseem ceeb yuav coj koj hauv kev txiav txim siab hauv lub neej thiab ua rau koj taug qab. Qhov tseem ceeb tshaj plaws, qhov tseem ceeb tshaj plaws yuav ua rau koj ntseeg siab hais tias "tsis yog." Lawv pab koj txheeb xyuas qhov xav tau tiag tiag hauv koj lub neej, piv rau lwm tus xav tias tseem ceeb.
