Video: Puas yog tus ntoo khaub lig koom nrog Cartesian cov khoom?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Ob tus koom muab tib yam tshwm sim. Hla - koom yog SQL99 koom thiab Cartesian khoom yog Oracle Proprietary koom . A ntoo khaub lig - koom uas tsis muaj 'qhov twg' clause muab rau Cartesian khoom . Cartesian khoom result-set muaj tus naj npawb ntawm kab hauv thawj lub rooj, muab faib los ntawm cov kab hauv ob lub rooj.
Kuj paub, tus ntoo khaub lig koom ua dab tsi?
Hauv SQL, lub CROSS JOIN yog siv los ua ke txhua kab ntawm thawj lub rooj nrog txhua kab ntawm lub rooj thib ob. Nws tseem hu ua Cartesian koom txij li thaum nws rov qab Cartesian cov khoom ntawm cov kab ntawm kab los ntawm cov rooj sib koom.
Kuj Paub, koj sau tus ntoo khaub lig koom li cas? Yog siv qhov twg nrog CROSS JOIN , nws ua haujlwm zoo li INNER Koom . Lwm txoj hauv kev kom ua tiav cov txiaj ntsig zoo ib yam yog siv cov npe kab sib cais los ntawm cov kab lus tom qab SELECT thiab hais txog cov npe ntawm lub rooj koom nrog, tom qab NTAWM kab lus. Piv txwv: Ntawm no yog ib qho piv txwv ntawm hla koom hauv SQL ntawm ob lub rooj.
Dhau li ntawd, Cartesian koom nrog SQL yog dab tsi?
A Cartesian koom los yog Cartesian khoom yog ib koom ntawm txhua kab ntawm ib lub rooj rau txhua kab ntawm lwm lub rooj. Qhov no feem ntau tshwm sim thaum tsis muaj qhov sib txuam koom kab lus tau teev tseg. Piv txwv li, yog tias rooj A nrog 100 kab yog koom nrog rooj B nrog 1000 kab, a Cartesian koom yuav rov 100,000 kab.
Cartesian yog dab tsi hauv database?
Cov Cartesian cov khoom, tseem hu ua kev sib koom ua ke, rov qab tag nrho cov kab hauv txhua lub rooj uas tau teev tseg hauv cov lus nug. Txhua kab hauv thawj lub rooj yog ua ke nrog tag nrho cov kab hauv lub rooj thib ob. Qhov no tshwm sim thaum tsis muaj kev sib raug zoo ntawm ob lub rooj.
Pom zoo:
Dab tsi ntawm algorithms xav kom tus neeg xa khoom thiab tus neeg txais kev sib pauv hloov tus yuam sij zais cia uas siv los xyuas kom meej qhov tsis pub lwm tus paub ntawm cov lus?
Dab tsi ntawm algorithms xav kom tus neeg xa khoom thiab tus neeg txais kev sib pauv pauv tus yuam sij zais cia uas siv los xyuas kom tsis pub leej twg paub cov lus? Kev piav qhia: Symmetrical algorithms siv tib tus yuam sij, tus yuam sij zais cia, los encrypt thiab decrypt cov ntaub ntawv. Tus yuam sij no yuav tsum tau muab qhia ua ntej ua ntej kev sib txuas lus tuaj yeem tshwm sim
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