Paub database. Cov kev xav ntawm ib tug paub database

Lub rov tshwm sim ntawm computer technology nyob rau hauv peb niaj hnub ntaub ntawv cim ib kiv puag ncig nyob rau hauv tag nrho cov spheres ntawm tib neeg kev ua si. Tab sis rau tag nrho cov ntaub ntawv tsis ua ruaj pov tseg nyob rau hauv lub Internet, twb yees ua los ntawm lub database system, nyob rau hauv uas cov ntaub ntawv yog txheeb, systematized, nrog rau cov tshwm sim hais tias lawv yog ib qho yooj yim mus nrhiav tau thiab xa lub tom ntej ua. Muaj peb lub ntsiab ntau yam - faib database paub, hierarchical, network.

yuav tsum muaj qauv

Rov qab mus rau cov emergence ntawm databases, nws yuav tsum tau hais tias tus txheej txheem no yog heev, nws originates nrog txoj kev loj hlob ntawm ib tug programmable ntaub ntawv ua cov khoom. Nws yog tsis xav tsis thoob hais tias tus naj npawb ntawm cov qauv tam sim no nce mus txog ntau dua 50, tab sis lub ntsiab sawv daws yuav pom tau hais tias yuav xaab, paub thiab network, uas yog tseem lug siv nyob rau hauv xyaum. Yuav ua li cas lawv sawv cev rau?

Xaab siab database muaj ib tsob ntoo cov qauv thiab yog muaj li ntawm cov ntaub ntawv sib txawv ntawm cov theem ntawm uas muaj kev sib txuas lus. Network database qauv yog ib tug ntau nyuab qauv. Nws qauv tsa ib tug hierarchy, thiab lub tswvyim txhab thiab zoo tuaj. Qhov txawv nruab nrab ntawm lawv yog hais tias lub roj ntsha hierarchical cov ntaub ntawv ua qauv yuav txuas nrog tsuas yog ib txwv zeej txwv koob, thaum lub network yuav tsum tau ob peb. Tus qauv ntawm ib tug paub database yog ntau npaum li cas complex. Yog li ntawd, nws yuav tsum tau rhuav nyob rau hauv ntau yam.

Cov yooj yim lub tswvyim ntawm ib tug paub database

Cov qauv no yog tsim nyob rau hauv 1970 los ntawm Dr. Edgar F. Codd science. Nws yog ib tug txawj cob qhia cov lus uas muaj teb uas piav qhia txog cov ntaub ntawv, cov kev sib raug nrog txhua lwm yam, ua hauj lwm ua rau lawv, thiab feem ntau cov tseem ceeb - cov kev cai uas tau lees tias lawv cov ntseeg. Yog vim li cas nws yog hu ua tus paub qauv? Nws yog raws li nyob rau hauv cov kev sib raug (los ntawm lub Latin. Relatio) ntawm cov ntaub ntawv. Muaj ntau ntau cov ntsiab lus txhais ntawm no hom ntawm database. Paub ntxhuav uas muaj ntaub ntawv yog yooj yim npaum li mus npaj thiab muab kev kho mob, es tsis yog ib tug network los yog xaab qauv. Yuav ua li cas koj ua li cas? Nws yog txaus kom paub tias cov nta, cov qauv qauv thiab thaj chaw ntawm lub paub ntxhuav.

Tus txheej txheem ntawm modeling thiab yooj yim hais

Nyob rau hauv thiaj li yuav tsim koj tus kheej database, koj yuav tsum siv ib qho ntawm cov modeling cov cuab yeej xav nrog dab tsi uas koj xav tau mus ua hauj lwm, los tsim ib tug paub lus thiab ib thiab ntau yam txuas ntawm cov ntaub ntawv chaw rau sau cov cell thiab teem lub thawj los yog txawv teb chaws tuav.

Modeling ntxhuav thiab vim paub databases yog ua los ntawm free cuab yeej zoo li Workbench, phpmyadmin, Case Studio, dbForge Studio. Tom qab ncauj lus kom ntxaws tsim kom txuag tau tus duab tiav lawm paub cov qauv thiab txhais nws rau hauv ib tug SQL-npaj code. Rau ntawm no theem, koj yuav pib ua hauj lwm nrog cov ntaub ntawv sorting, ua thiab systematization.

Nta ntawm cov qauv thiab cov ntsiab lus uas txuam nrog rau cov paub cov qauv

Txhua qhov chaw nyob rau hauv nws tus kheej txoj kev piav qhia txog nws hais, ces kuv yuav muab ib tug me ntsis hint rau tsawg tsis meej pem:

• paub daim ntawv lo = xwm;
• layout = cwj pwm npe = golf = kem header chaw;
• qhov chaw piv txwv li = tuple = cov ntaub ntawv = phaj kab;
• attribute = tus nqi = cell chaw teb.

Mus rau ib tug paub database zog yuav tsum tau paub txog ib co pib kawm nws muaj thiab rau cov uas lawv yog npaj.

1. Essence. Rooj paub database yuav ua tau ib tug, los yog tej zaum yuav ib tug txheej ntawm lub rooj uas characterize piav khoom cia nyob rau ntawd los ntawm cov ntaub ntawv. Lawv muaj ib tug tsau tooj ntawm liaj teb, thiab ib tug nce mus nce los tus naj npawb ntawm nkag. Rooj paub qauv database yog muaj li ntawm cov hlua, cwj pwm, thiab layout.
2. Rau cov ntaubntawv povthawj - ib tug kuj sib txawv thiab tus naj npawb ntawm kab uas tso saib cov ntaub ntawv uas tuab lub piav kwv. Numbering nkag ua tau los ntawm lub system.
3. Cwj Pwm - Cov ntaub ntawv uas qhia ib qho NTSIAB txhua.
4. Teb. Nws yog ib qhov chaw kem. Lawv tus naj npawb - qhov chaw ruaj tus nqi yog muab thaum lub sij hawm lub creation los yog kev hloov kho ntawm lub rooj.

Tam sim no, kev paub txog lub constituent ntsiab ntawm lub rooj, koj yuav tau tsiv mus rau lub zog ntawm cov paub cov qauv database:

• Lub essence ntawm ob-dimensional paub database. Vim li no cov cuab yeej nrog lawv yooj yim prodelyvat ntau zajlus kom thiab xaam ua hauj lwm.
• Qhov kev txiav txim ntawm attribute qhov tseem ceeb thiab cov ntaub ntawv nyob rau hauv ib tug paub lus yuav ua tau arbitrary.
• Kem nyob rau hauv ib paub cov lus yuav tsum muaj nws tus kheej cim npe.
• Tag nrho cov ntaub ntawv nyob rau hauv cov kem yeej tseem zoo muaj ib taag ntev thiab tib yam.
• Tej nkag nyob rau hauv essence yog xam raws li ib daim ntawm cov ntaub ntawv.
• Num Cheebtsam ntawm lub kab yog cim. Cov paub xwm yog tsis muaj duplicate kab.

Raws li lub zog ntawm cov paub database, nws yog to taub hais tias qhov tseem ceeb ntawm tej cwj pwm uas yuav tsum tau ntawm tib yam, ntev. Xav txog ib tug cwj pwm tseem ceeb.

Lub ntsiab yam ntxwv ntawm lub teb ntawm paub databases

Teb npe yuav tsum muaj cim hauv ib qhov chaw. Lub hom cwj pwm los yog teb ntawm paub databases piav ib qeb ntawm cov ntaub ntawv khaws tseg nyob rau hauv qhov chaw teb. Teb paub database yuav tsum muaj ib tug taag loj, me, uas yog xam nyob rau hauv cov cim. Tsis thiab format lub attribute qhov tseem ceeb txhais tau lub sijhawm ntawm txoj kev kho lawv cov ntaub ntawv. Tsis tau muaj yog xws li ib tug tshaj plaws raws li ib tug "daim npog qhov ncauj" los yog "tswv yim template". Nws yog tsim los mus txiav txim lub configuration ntawm cov ntaub ntawv tswv yim nyob rau hauv lub attribute nqi. Yeej ntawm tsis ncaj ncees lawm cov ntaub ntawv hom ntawm cov ntaub ntawv yuav tsum tau muab rau ib tug kab qhia nyob rau hauv lub teb. Tsis tas li ntawd nyob rau hauv lub teb ntsiab yog ib co kev txwv - tej yam kev mob rau koj lub checking cov neeg thiab precision ntawm cov ntaub ntawv nkag teb chaws. Muaj yog ib tug yuav tsum attribute nqi uas uniquely muaj yuav tsum tau sau nrog cov ntaub ntawv. Ib txhia cwj pwm kab tej zaum yuav tau sau nrog thov-qhov tseem ceeb. Pub mus rau hauv lub empty cov ntaub ntawv teb tej cwj pwm. Raws li nrog rau ib tug kab laum daim ntawv, yog qhov tseem ceeb uas yog lawm ua tus sau cia los ntawm lub system - qhov no yog lub neej ntawd cov ntaub ntawv. Rau kom cov kev tshawb fawb rau tej ntaub ntawv npaj indexed teb.

Scheme dimensional paub database rooj

Rau ib ncauj lus kom ntxaws kev nkag siab ntawm lub tswj system qauv siv SQL zoo tshaj plaws yuav tau xav txog lub tswvyim li ib qho piv txwv. Peb twb paub tias dab tsi yog ib tug paub database. Kev nkag teb chaws nyob rau hauv txhua lub rooj - ib zaug xwb cov ntaub ntawv keeb. Yuav kom tiv thaiv cov ntaub ntawv redundancy, tsim nyog rau normalize lub lag luam.

Cov kev cai ntawm normalization ntawm paub xwm

1. Tus nqi ntawm lub teb lub npe rau ib tug paub lus yuav tsum muaj cim, ib tug ntawm ib tug zoo (Npe qub Form - 1NF).

2. Rau ib lub rooj uas twb raug txo kom 1NF, uas tsis yog-paub lub npe ntawm tej kem yuav nyob rau ib tug tshwj xeeb cov lus qhia (2NF).

3. Rau tag nrho cov ntxhuav uas twb muab cia rau hauv 2NF, uas tsis yog-paub txhua teb yuav ua tau ywj siab ntawm lwm yam lam caij tseem ceeb (3NF chaw).

Databases: paub mus ntawm lub rooj

Muaj 2 lub ntsiab hom ntawm kev sib raug ntawm paub ntsiav tshuaj:

• "Ib tug-ntau". Raws li tshwm sim thaum ib tug tseem ceeb rooj nkag №1 ntau zaus ntawm lub thib ob qhov chaw. Ntsiab icon nyob rau hauv ib tug ntawm qhov xaus ntawm lub kos kab hais tias lub tshuaj yog nyob rau sab ntawm "ib tug", lub lwm kawg ntawm tus kab no feem ntau yog ib lub cim ntawm infinity cim.

• Kev sib txuas lus "ntau-ntau" tsim nyob rau hauv cov ntaub ntawv ntawm ob peb kab ib zajlus kom qhov chaw qhia tau meej heev kev sis raug zoo nrog ib tug xov tooj ntawm cov ntaub ntawv ntawm lwm lub rooj.
• Yog hais tias ob cov chaw muaj ib tug concatenation ntawm "ib tug rau ib", nws txhais tau tias tseem ceeb qhia ntawm ib lub rooj yog tam sim no nyob rau hauv lub qhov chaw, ces nws yog tsim nyog los tshem tawm ib yam ntawm lub rooj, nws yog superfluous. Tab sis tej zaum tsuas yog rau cov kev ruaj ntseg cov txhob txwm cais ob tug lwm qhov chaw. Yog li ntawd, hypothetically, kev twb kev txuas ntawm "ib tug rau ib" yuav nyob ua ib ke.

Lub hav zoov ntawm cov yuam sij nyob rau hauv ib tug paub database

Thawj thiab theem nrab tuav paub txog tej database kev sib raug zoo. Paub cov ntaub ntawv sib txuas lus qauv yuav muaj tsuas yog ib tus neeg sib tw tseem ceeb, nws yuav tsum thawj tseem ceeb. Yuav ua li cas yog nws? Primary tseem ceeb - ib kem los yog ib tug txheej ntawm tej cwj pwm ntawm cov essence, los ntawm kev uas koj muaj peev xwm nce mus rau ib tug kev cov ntaub ntawv kab. Nws yuav tsum muaj cim, lub tsuas yog ib, thiab nws teb tsis tau muaj thov qhov tseem ceeb. Yog hais tias cov thawj tseem ceeb muaj tsuas yog ib attribute, ces nws yog hais tias yuav tsum yooj yim, txwv tsis pub yuav.

Dhau li ntawm tus thawj tseem ceeb, tshwm sim thiab sab nraud (txawv teb chaws tseem ceeb). Muaj ntau yam tsis to taub dab tsi txawv nruab nrab ntawm lawv. Cia peb kawm lawv nyob rau hauv ntau yam raws li ib qho piv txwv. Yog li ntawd, muaj ob lub rooj: "Dean" thiab "Cov menyuam kawm ntawv". Lub essence ntawm "Dean" muaj lub teb: "ID tus menyuam kawm ntawv", "lub npe" thiab "Group." Rooj "Cov menyuam kawm ntawv" muaj cov attribute qhov tseem ceeb xws li "lub npe", "Group" thiab "nruab nrab". Yog li ntawd raws li ib tug me nyuam kawm ntawv ID muaj peev xwm tsis yuav tib yam rau ib tug ob peb cov tub ntxhais kawm, nws yog ib lub teb tau los ua tus thawj tseem ceeb. "Lub npe" thiab "Group" los ntawm lub "cov tub ntxhais kawm" ntawm lub rooj tej zaum yuav tib yam rau ib tug ob peb tus neeg, lawv xa mus rau cov me nyuam kawm ntawv tus ID naj npawb los ntawm cov essence ntawm "Dean", yog li lawv muaj peev xwm yuav siv tau raws li ib tug txawv teb chaws tseem ceeb.

Ib qho piv txwv ntawm paub database qauv

Rau clarity, peb muab ib tug piv txwv yooj yim ntawm ib tug paub database qauv uas muaj ob qhov chaw. Muaj yog ib lub rooj uas muaj lub npe "Dean".

Nws yog tsim nyog los nqa tawm kev twb kev txuas kom tau ib tug tag nrho cov paub database. Nkag "IN-41" raws li "IN-72", tej zaum yuav tam sim no ntau tshaj li ib zaug nyob rau hauv lub rooj "Dean" raws li lub xeem, lub npe thiab patronymic ntawm cov menyuam kawm ntawv, nyob rau hauv uas tsis tshua muaj mob, yuav tsum yog tib yam, yog li no teb tsis tau los mus ua kom cov thawj tseem ceeb. lub essence ntawm "Cov menyuam kawm ntawv" yuav qhia.

Raws li peb tau pom, lub hom paub database teb txawv kiag li. Tam sim no raws li cov recordings thiab cov ua cim. Yog li ntawd, cov attribute chaw yuav tsum qhia tias tus nqi ntawm integer, char, vachar, hnub tim thiab lwm tus neeg. Nyob rau hauv lub "Dean" cim nqi yog ib lub xwb tub ntxhais kawm ntawv ID. Daim teb no yuav tsum noj raws li ib tug thawj tseem ceeb. Lub npe, artist, thiab xov tooj ntawm cov essence ntawm "Cov menyuam kawm ntawv" yuav tsum noj raws li ib tug txawv teb chaws tseem ceeb referencing lub ID ntawm tus menyuam kawm ntawv. Cov kev twb kev txuas yog tsim los pab. Qhov no yog ib qho piv txwv ntawm ib tug kev sib txuas lus qauv ntawm "ib tug rau ib". Hypothetically, yog ib lub ntxiv ntxhuav, lawv muaj peev xwm muab tau yooj yim ua ke rau hauv ib qhov chaw. Mus rau ID-tus naj npawb ntawm cov tub ntxhais kawm tsis ua universally paub, nws yog heev tau hais tias muaj ob lub rooj.