Cov txheej txheem:
Video: Vim li cas cov ntaub ntawv tsis raug cai yog teeb meem?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Ib tug tsis zoo normalized database thiab cov rooj ua haujlwm tsis zoo tuaj yeem ua rau teeb meem xws li los ntawm ntau lub disk I / O thiab cov kev ua haujlwm tsis zoo tom ntej kom tsis raug cov ntaub ntawv . Ib qho xwm txheej tsis raug cai tuaj yeem ua rau muaj qhov dav cov ntaub ntawv redundancy, uas tso lub nra rau tag nrho cov kev pab cuam uas hloov cov cov ntaub ntawv.
Nyob rau hauv no txoj kev, dab tsi characterizes unnormalized ntaub ntawv?
Unnormalized daim ntawv (UNF), tseem hu ua ib tsis zoo li qub Kev sib raug zoo lossis tsis yog thawj daim ntawv (NF2), yog ib qho yooj yim database cov ntaub ntawv qauv (lub koom haum ntawm cov ntaub ntawv nyob rau hauv ib tug database) tsis muaj cov efficiency ntawm database normalization.
Tom qab, lo lus nug yog, yuav ua li cas yog tias koj tsis normalize lub database? Tsis- normalized cov ntxhuav feem ntau txhais tau hais tias tib cov ntaub ntawv khaws cia hauv ntau dua ib qho chaw. Yog Qhov no yog qhov teeb meem, tsis tuaj yeem thov code los tiv thaiv nws, nws muaj peev xwm heev uas ib qho ntawm cov txiaj ntsig yuav raug hloov kho yam tsis tau hloov kho tag nrho cov ntawv luam ntawm tus nqi tib yam hauv lwm cov ntxhuav.
Cov neeg kuj nug, dab tsi yog qhov zoo ntawm normalizing ib tug database?
Cov cov txiaj ntsig ntawm normalization suav nrog: Kev tshawb nrhiav, txheeb xyuas, thiab tsim cov indexes sai dua, vim cov ntxhuav yog nqaim, thiab ntau kab haum rau ntawm nplooj ntawv cov ntaub ntawv. Koj feem ntau muaj rooj ntau dua. Koj tuaj yeem muaj ntau pawg ntsuas (ib lub rooj), yog li koj tau txais kev hloov pauv ntau dua hauv cov lus nug.
Dab tsi yog qhov tsis zoo ntawm normalization?
Nov yog qee qhov tsis zoo ntawm normalization:
- Txij li cov ntaub ntawv tsis yog duplicated, lub rooj koom yuav tsum tau. Qhov no ua rau cov lus nug nyuaj, thiab yog li kev nyeem ntawv qeeb qeeb.
- Txij li kev koom nrog yuav tsum tau ua, indexing tsis ua haujlwm zoo.
Pom zoo:
Vim li cas cov ntaub ntawv tiaj tus tsis zoo dua li cov ntaub ntawv sib raug zoo?
Ib lub rooj ua ntaub ntawv tiaj tus yog qhov tseem ceeb rau kev sau cov ntaub ntawv tsawg. Tab sis cov ntaub ntawv loj loj tuaj yeem ua tsis tau raws li nws siv ntau qhov chaw thiab nco dua li cov ntaub ntawv sib txheeb. Nws kuj yuav tsum tau muab cov ntaub ntawv tshiab ntxiv txhua zaus koj nkag mus rau cov ntaub ntawv tshiab, qhov kev sib raug zoo database tsis
Cov teeb meem dab tsi yog tus qauv qauv daws teeb meem?
Cov qauv zoo yog siv los daws cov teeb meem uas tej zaum yuav (los yog pom tias lawv yuav) raug coj los siv lossis daws los ntawm cov tswv yim sib txawv thiab uas muaj cov lus qhia meej meej rau cov xwm txheej zoo li no
Vim li cas kem taw qhia cov ntaub ntawv khaws cia ua cov ntaub ntawv nkag ntawm disks sai dua li kab qhia cov ntaub ntawv khaws cia?
Kem oriented databases (aka columnar databases) yog qhov tsim nyog rau kev ntsuas kev ua haujlwm ntau dua vim tias cov ntaub ntawv hom ntawv (kem hom) qiv nws tus kheej kom nrawm dua cov lus nug ua - scans, aggregation thiab lwm yam. Ntawm qhov tod tes, kab oriented databases khaws ib kab (thiab tag nrho nws. kab) contiguously
Dab tsi yog cov teeb meem ntawm kev tswj cov ntaub ntawv hauv cov ntaub ntawv ib txwm muaj?
Nyob rau tib lub sijhawm, qhov kev tswj hwm cov ntaub ntawv ib puag ncig tsim teeb meem xws li cov ntaub ntawv rov ua dua thiab tsis sib xws, cov kev pab cuam-cov ntaub ntawv dependence, inflexibility, tsis muaj kev ruaj ntseg, thiab tsis muaj cov ntaub ntawv sib qhia thiab muaj
Dab tsi yog qhov xav tau rau cov chav kawm paub daws teeb meem thiab kev paub daws teeb meem?
Cov chav kawm Abstract. Abstract (uas Java txhawb nrog cov ntsiab lus paub daws teeb meem) txhais tau hais tias chav kawm lossis txoj hauv kev lossis teb lossis txhua yam tsis tuaj yeem ua tam sim (uas yog, tsim) qhov twg nws tau txhais. Lwm yam khoom yuav tsum instantiate cov khoom nyob rau hauv nqe lus nug. Yog tias koj ua ib chav kawm abstract, koj tsis tuaj yeem instantiate ib yam khoom los ntawm nws