Video: Qhov twg yog kev sib raug zoo dua?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
A kev sib raug zoo nruab nrab ntawm ob qhov chaw ntawm qhov chaw zoo sib xws yog hu ua a kev sib raug zoo . Hauv lwm lo lus, a kev sib raug zoo yeej ib txwm nyob ntawm qhov tshwm sim hauv ob qhov chaw sib txawv. Txawm li cas los xij, nws muaj peev xwm rau tib lub koom haum koom nrog kev sib raug zoo . Qhov no yog hu ua a kev sib raug zoo.
Kuj paub, qhov kev sib raug zoo recursive muab piv txwv yog dab tsi?
Cov kev sib raug zoo yog a kev sib raug zoo nruab nrab ntawm ib qho chaw thiab nws tus kheej. Rau piv txwv peb-ing lub koom haum PERSON, a kev sib raug zoo tuaj yeem siv los qhia ib tus neeg thiab nws tus SIBLING.
Ib tug kuj yuav nug, dab tsi yog qhov degree ntawm kev sib raug zoo recursive? A kev sib raug zoo (los yog UNARY Kev sib raug zoo ) yog ib qho uas tib lub koom haum koom nrog ntau tshaj ib zaug hauv lub kev sib raug zoo . Txij li thaum tus neeg ua haujlwm raug tswj hwm los ntawm tus thawj tswj hwm (uas yog nws tus kheej yog tus neeg ua haujlwm), yog li ntawd, qhov degree ntawm kev sib raug zoo yog 1.
Xav txog qhov no, kev sib raug zoo ntawm tus kheej yog dab tsi?
Thaum tus yuam sij txawv teb chaws siv tus yuam sij niam txiv (Primary key) ntawm tib lub rooj, ces nws yog hu ua a SELF REFERENTIAL LOSSIS RECURSIVE RELATIONSHIP . Kab Manager_No nyob rau hauv lub Employee rooj yog ib tug txawv teb chaws tus yuam sij uas yuav siv sij hawm nws qhov tseem ceeb ntawm kab Employee_No ntawm tib lub rooj Employee.
Dab tsi yog qhov recursive saib?
Tag nrho cov koom nrog sab nrauv siv tau thaum siv hauv ib recursive nqe lus tsuas yog hais tias tsis yog sab hauv los yog lub rooj sab nrauv nyob rau sab nrauv koom txhais yog tus recursive saib raug txhais los yog 1 ntawm nws cov kev sib raug zoo. Nyob rau hauv lwm yam lus, ib tug tag nrho sab kev koom siv nyob rau hauv ib recursive lus nug tsis tuaj yeem hla rov ua dua.
Pom zoo:
Qhov kev xav ntawm kev paub txog kev loj hlob twg yog tsom rau kev sib raug zoo?
Lev Vygotsky
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
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