Video: Qhov twg hauv qab no sawv cev rau qhov zoo ntawm tus yuam sij surrogate?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
A surrogate key yog ib qho tshwj xeeb, DBMS-muab tus cim siv los ua thawj tus yuam sij ntawm kev sib txheeb. Nws qhov zoo yog: (1) Lawv txawv nyob rau hauv lub rooj thiab yeej tsis hloov. (2) Lawv raug xa mus thaum kab yog tsim thiab rhuav tshem thaum kab yog tshem tawm.
Ib yam li ntawd, nws raug nug, qhov twg hauv qab no yog qhov zoo ntawm kev siv tus yuam sij surrogate?
Hauv qab no yog ib co qhov zoo ntawm kev siv tus yuam sij surrogate nyob rau hauv cov ntaub ntawv warehouse: Nrog kev pab los ntawm tus yuam sij surrogate , koj tuaj yeem sib sau ua ke cov ntaub ntawv sib txawv rau cov ntaub ntawv warehouse yog tias lawv tsis muaj ntuj lossis kev lag luam cov yuam sij . Koom nrog cov rooj (qhov tseeb thiab qhov ntev) siv tus yuam sij surrogate yog sai li no ua tau zoo dua.
Dab tsi yog tus yuam sij surrogate thiab vim li cas siv lawv? A tus tseem ceeb yog a tus yuam sij uas tsis muaj cov ntsiab lus lossis kev lag luam. Nws yog tsim "artificially" thiab tsuas yog rau lub hom phiaj ntawm kev txheeb xyuas cov ntaub ntawv. Feem ntau siv version ntawm a tus tseem ceeb yog ib qho kev nce zuj zus los yog "counter" tus nqi (piv txwv li 1, 2, 3).
Tom qab ntawd, dab tsi yog qhov zoo ntawm tus yuam sij surrogate Vim li cas peb tsis tuaj yeem siv cov yuam sij ntuj?
Surrogate yuam sij yuav tsis ua hloov kho raws sijhawm. Surrogate yuam sij feem ntau yog cov lej, uas tsuas yog xav tau 4 bytes khaws cia, yog li thawj tus yuam sij index structure yuav ua me me dua lawv natural key counterparts. Muaj cov qauv ntsuas me me txhais tau tias kev ua tau zoo dua rau JOIN cov haujlwm.
Dab tsi yog siv los ua tus yuam sij surrogate?
A tus tseem ceeb yog txhua kab los yog kab ke uas tuaj yeem tshaj tawm tias yog thawj tus yuam sij es tsis yog "tiag" lossis ntuj tus yuam sij . Hom ntau tshaj ntawm tus tseem ceeb yog ib qho incrementing integer, xws li auto_increment kem hauv MySQL, lossis ib ntu hauv Oracle, lossis kab ke tus kheej hauv SQL Server.
Pom zoo:
Ib tus yuam sij tseem ceeb puas tuaj yeem muaj ob tus yuam sij txawv teb chaws?
Nws yog qhov zoo kawg nkaus kom muaj ob kab ntawv tseem ceeb txawv teb chaws xa mus rau tib lub ntsiab lus tseem ceeb hauv ib lub rooj sib txawv vim tias txhua tus nqi tseem ceeb txawv teb chaws yuav siv cov ntaub ntawv sib txawv hauv cov lus hais
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
Dab tsi yog tus yuam sij ntiag tug thiab pej xeem tus yuam sij hauv Blockchain?
Thaum ib tug neeg xa koj cryptocoins hla Blockchain, lawv tau xa lawv mus rau qhov hashed version ntawm qhov hu ua "Public Key". Muaj lwm tus yuam sij uas zais ntawm lawv, uas yog hu ua "Private Key." Qhov Private Key no yog siv los muab Public Key
Koj txhais li cas los ntawm tus yuam sij ntiag tug thiab pej xeem tus yuam sij cryptography?
Nyob rau hauv pej xeem tus yuam sij cryptography, ob tus yuam sij yog siv, ib tug yuam sij yog siv rau encryption thiab thaum lwm yam yog siv rau decryption. 3. Nyob rau hauv private keycryptography, tus yuam sij yog khaws cia tsis pub leejtwg paub. Nyob rau hauv pej xeem tus yuam sij cryptography, ib qho ntawm ob tus yuam sij yog khaws cia tsis pub leejtwg paub
Cov lus txib twg yog siv los tshem tawm qhov tas sij hawm los ntawm tus yuam sij hauv Redis?
Redis Keys Commands Sr.No Command & Description 10 PERSIST tus yuam sij Tshem tawm qhov tas sij hawm ntawm tus yuam sij. 11 PTTL yuam sij Tau txais lub sij hawm seem hauv cov yuam sij tas sij hawm hauv milliseconds. 12 TTL tus yuam sij Tau txais cov sij hawm seem hauv cov yuam sij tas sij hawm. 13 RANDOMKEY Rov qab ib qho yuam sij los ntawm Redis