Cov txheej txheem:
Video: Dab tsi yog qee qhov tsis zoo ntawm lub sijhawm stamping txoj hauv kev rau kev tswj hwm kev sib raug zoo?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Cov qhov tsis zoo ntawm lub sijhawm stamping txoj hauv kev yog tias txhua tus nqi khaws cia hauv cov ntaub ntawv xav tau ob qho ntxiv lub sij hawm stamp teb: ib rau lub xeem sij hawm daim teb tau nyeem thiab ib qho rau qhov hloov tshiab kawg. Lub sijhawm stamping yog li tsub kom nco xav tau thiab cov ntaub ntawv tus txheej txheem nyiaj siv ua haujlwm.
Yog li ntawd, dab tsi yog qhov teeb meem ntawm kev ua tiav ntawm kev sib pauv?
Thaum twg kev sib pauv hloov yog raug tua nyob rau hauv ib tug uncontrolled yam, ntau teeb meem tuaj yeem tshwm sim. Kev tswj hwm concurrency muaj peb lub ntsiab hauv qab no teeb meem : Poob kho tshiab. Cov ntawv nyeem qias neeg (lossis cov ntaub ntawv tsis raug cai).
Ib yam li ntawd, lub kaw lus tsim cov ntawv teev sijhawm li cas? Feem ntau, daim ntawv teev sijhawm tus nqi raug muab tso rau hauv qhov kev txiav txim uas cov kev hloov pauv raug xa mus rau qhov system . Cov kev lag luam raug tswj kom lawv zoo li khiav hauv ib daim ntawv teev sijhawm xaj. Daim ntawv teev sijhawm tuaj yeem yog tsim tawm los ntawm incrementing ib logical counter txhua lub sij hawm ib tug tshiab pauv pib.
Tsis tas li ntawd, koj ua li cas tswj concurrency hauv database?
Concurrency tswj yog muab nyob rau hauv ib tug database rau:
- (i) tswj kev sib cais ntawm kev lag luam.
- (ii) khaws cia cov ntaub ntawv sib xws los ntawm kev sib koom ua ke khaws cia ua tiav kev lag luam.
- (iii) daws teeb meem nyeem-sau thiab sau-nyeem tsis sib haum.
Vim li cas thiaj xav tau kev tswj hwm nyiaj txiag?
Yog vim li cas siv Concurrency tswj Txoj kev yog DBMS: Txhawm rau siv Isolation los ntawm kev sib cais ntawm kev tsis sib haum xeeb. Txhawm rau daws teeb meem nyeem-sau thiab sau-sau teeb meem. Txhawm rau khaws cov ntaub ntawv sib xws los ntawm kev khaws cia cov kev ua haujlwm tsis tu ncua.
Pom zoo:
Qhov twg hauv qab no yog suav tias yog kev tswj hwm kev ua haujlwm ntawm kev tswj hwm database DBMS)?
Databases uas nqa lawv cov ntaub ntawv nyob rau hauv daim ntawv ntawm cov ntxhuav thiab uas sawv cev rau kev sib raug zoo siv txawv teb chaws yuam sij yog hu ua discrete databases. Kev tswj hwm kev ua haujlwm ntawm kev tswj hwm qhov system (DBMS) suav nrog thaub qab cov ntaub ntawv database
Vim li cas kev sib raug zoo algebra siv nyob rau hauv kev sib raug zoo database tswj?
RELATIONAL ALGEBRA yog ib hom lus nug uas siv dav heev. Nws sau cov xwm txheej ntawm kev sib raug zoo raws li kev tawm tswv yim thiab muab qhov tshwm sim ntawm kev sib raug zoo raws li cov zis. Nws siv ntau yam haujlwm los ua qhov haujlwm no. Relational algebra operations yog ua recursively ntawm kev sib raug zoo
Dab tsi yog qhov txawv ntawm kev sib raug zoo unary kev sib raug zoo binary thiab kev sib raug zoo ternary?
Kev sib raug zoo tsis sib xws yog thaum ob tus neeg koom hauv kev sib raug zoo yog tib lub koom haum. Piv txwv li: Cov ncauj lus yuav yog qhov yuav tsum tau ua ua ntej rau lwm yam kev kawm. Kev sib raug zoo ternary yog thaum peb lub koom haum koom nrog kev sib raug zoo
Dab tsi yog qhov txawv ntawm kev sib raug zoo thiab tsis muaj kev sib raug zoo databases?
Qhov sib txawv loj ntawm lawv yog li cas lawv tuav cov ntaub ntawv. Relational databases are structured.Non-relational databases are document-oriented. Qhov no hu ua cov ntaub ntawv hom cia tso cai ntau 'qeb' ntawm cov ntaub ntawv khaws cia hauv ib qho kev tsim lossis Cov Ntaub Ntawv
Qhov kev tswj hwm twg suav nrog kev tswj hwm lub cev thiab kev tswj hwm?
Piv txwv suav nrog kev tswj lub cev xws li laj kab, xauv, thiab lub tswb nrov; kev tswj xyuas xws li antivirus software, firewalls, thiab IPSs; thiab kev tswj hwm kev tswj hwm xws li kev sib cais ntawm lub luag haujlwm, kev faib cov ntaub ntawv, thiab kev tshuaj xyuas