Cov txheej txheem:
Video: Dab tsi yog qhov kev sib raug zoo algebra ua haujlwm?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Tsib theem pib kev ua haujlwm hauv kev sib raug zoo algebra : Kev Xaiv, Kev Tshaj Tawm, Cartesian khoom, Union, thiab Teeb Qhov Sib Txawv.
Tom qab ntawd, kev sib raug zoo algebra yog dab tsi?
Relational algebra yog ib tug txheej txheem query lus, uas yuav siv sij hawm ntawm kev sib raug zoo raws li cov tswv yim thiab yields piv txwv ntawm kev sib raug zoo raws li tso zis. Nws siv cov neeg ua haujlwm los ua cov lus nug. Tus neeg teb xov tooj tuaj yeem yog unary lossis binary. Lawv lees txais kev sib raug zoo raws li lawv cov tswv yim thiab tawm tswv yim kev sib raug zoo raws li lawv cov txiaj ntsig.
Dab tsi yog cov neeg ua haujlwm sib raug zoo? Relational Operators
- <: tsawg dua.
- <=: tsawg dua los yog sib npaug.
- >: ntau dua.
- >=: ntau dua los yog sib npaug.
- ==: sib.
- //: tsis sib npaug.
Tom qab ntawd, ib tug kuj yuav nug, dab tsi yog qhov kev sib raug zoo algebra ua haujlwm txhawb nqa hauv SQL?
Relational algebra tsuas yog muab lub hauv paus theoretical rau kev sib txheeb databases thiab SQL
- Cov neeg ua haujlwm hauv Relational Algebra.
- Qhov projection (π)
- Nco tseg: Los ntawm Default projection tshem tawm cov ntaub ntawv duplicate.
- Kev xaiv (σ)
- Nco tseg: xaiv tus neeg teb xov tooj tsuas yog xaiv cov tuples uas yuav tsum tau tab sis tsis tso rau lawv.
- Union (U)
- Teeb qhov txawv (-)
Dab tsi yog koom nrog hauv kev sib raug zoo algebra?
Xws li koom ua rau ob tus cwj pwm nyob rau hauv qhov kev sib raug zoo uas muaj qhov zoo ib yam. ? Ib tug natural koom yuav tshem tawm cov cwj pwm duplicate.
Pom zoo:
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 kev sib tshuam hauv kev sib raug zoo algebra?
INTERSECTION kev khiav hauj lwm nyob rau hauv RELATIONAL ALGEBRA. Kev sib tshuam ntawm teeb A thiab B = A ∩ B = {1, 6} Cov ntsiab lus uas muaj nyob rau hauv ob qho tib si A thiab B yuav tsuas muaj nyob rau hauv lub teeb tau los ntawm kev sib tshuam ntawm A thiab B
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
Dab tsi yog qee qhov tsis zoo ntawm lub sijhawm stamping txoj hauv kev rau kev tswj hwm kev sib raug zoo?
Qhov tsis zoo ntawm lub sij hawm stamping mus kom ze yog tias txhua tus nqi khaws cia hauv cov ntaub ntawv yuav tsum muaj ob lub sij hawm thwj ntxiv: ib qho rau lub sijhawm kawg ntawm daim teb tau nyeem thiab ib qho rau qhov hloov tshiab kawg. Lub sij hawm stamping yog li ua rau kom nco xav tau thiab cov ntaub ntawv ua haujlwm nyiaj siv ua haujlwm