Egciniwe zingubudlelwane. Umcabango database zingubudlelwane

Ukuvela ubuchwepheshe bama-computer ngemininingwane yethu yesimanje imakwe revolution yonke imikhakha yomsebenzi womuntu. Kodwa ukuze yonke imininingwane akubi imfucuza ngokungadingekile Inthanethi, yasungulwa uhlelo semininingwane, lapho izinto ihlelwa, systematized, futhi umphumela waba ukuthi kulula ukuthola bese uhambisa ukucutshungulwa okwalandela. Kukhona izinhlobonhlobo ezintathu eziyinhloko - ukwaba semininingwane zingubudlelwane ephethwe yisigungu sesonto, inethiwekhi.

onobuhle eliyisisekelo

Ukubuyela ukuvela yolwazi, kufanele kusho ukuthi le nqubo kwaba ngempela eziyinkimbinkimbi, ke kuvela ekuthuthukiseni a ehlelwe i-information processing imishini. Akumangazi ukuthi isibalo onobuhle okwamanje ifinyelela ezingaphezu kuka-50, kodwa abanendlela main abhekwa ephethwe yisigungu sesonto, zingubudlelwane nakunethiwekhi, okuyinto namanje kabanzi umkhuba. Yini abakubonisayo?

egciniwe phezulu has a isakhiwo esihlahleni futhi yakhiwa idatha abasemazingeni ahlukahlukene phakathi lapho kukhona ukukhulumisana. Uxhumano imodeli semininingwane yiphethini more xaka. isakhiwo sayo sifana yokwehlayo, futhi isikimu enwetshiwe ngcono. Umehluko phakathi kwabo ukuthi lezinceku phezulu onobuhle idatha kungahlanganiswa ukhokho eyodwa kuphela, kuyilapho inethiwekhi kungenzeka eziningana. Nesakhiwo zingubudlelwane semininingwane ithi ukuba yinkimbinkimbi kakhudlwana. Ngakho-ke, kufanele adiliza kabanzi.

Umqondo oyisisekelo database zingubudlelwane

Le modeli yasungulwa ngo-1970 nguDkt Edgar F. Codd isayensi. Kuyinto itafula ngokunengqondo yakhiwe imikhakha ezichaza idatha, ubudlelwano babo nomunye, imisebenzi eyenziwa kuwo, futhi okubaluleke - imithetho eziqinisekisa ubuqotho babo. Kungani-ke kubizwa ngokuthi imodeli zingubudlelwane? Kusekelwe ubudlelwane (kusukela Latin. Relatio) phakathi idatha. Kukhona izincazelo eziningi lokhu uhlobo egciniwe. amatafula zingubudlelwane ngolwazi kuba lula ukuhlela bese unikeza nemithi, kunokuba inethiwekhi noma imodeli phezulu. Wenzenjani ukukwenza? Kwanele ukwazi izici, isakhiwo imodeli nezakhiwo amatafula zingubudlelwane.

Inqubo yokwakheka nokulandelana eziyisisekelo izakhi

Ukuze udale database wakho siqu, kufanele usebenzise lamathuluzi ukumodeliswa ukucabanga ngalokho ulwazi okudingeka usebenzele, ukwakha itafula zingubudlelwane nezixhumanisi olulodwa futhi amaningi phakathi idatha izinhlangano ukugcwalisa iseli bese usetha okhiye eyinhloko noma angaphandle.

Ukumodela amatafula kanye nokwakha izizinda zingubudlelwane wenziwa ngokusebenzisa amathuluzi khulula like banebhentshi, phpmyadmin, Case Studio, dbForge Studio. Ngemva okuklama enemininingwane ukulondoloza ingcaca siphelile imodeli zingubudlelwane futhi kwisi ku ikhodi SQL-ngomumo. Kulesi sigaba, ungaqala ukusebenza idatha uphenya, ukucubungula systematization.

Izici isakhiwo kanye nemigomo ephathelene ne-imodeli zingubudlelwane

umthombo ngamunye ngendlela yalo uchaza izakhi zawo, ngakho ngingathanda ukukunika mfana omncane ngoba ukudideka kancane:

• ilebula zingubudlelwane = nemvelo;
• isakhiwo = igama lesichasiso = igalofu = ikholomu unhlokweni inhlangano;
• inhlangano Ngokwesibonelo = tuple = irekhodi = ipuleti umugqa;
• Imfanelo = inani = cell izinhlangano ensimini.

Ukuya zingubudlelwane semininingwane izakhiwo kufanele bazazi izingxenye ezithile eziyisisekelo ke yakhiwa futhi zona ahloselwe.

1. Essence. Ithebula semininingwane zingubudlelwane kungaba umuntu, noma kungaba iqoqo amatafula agcwele echazwe izinto egcinwe therein ngokusebenzisa idatha. Sinenkosi izinombolo ezihleliwe lamasimu, kanye nenombolo elibanzi okufakiwe. Ithebula imodeli zingubudlelwane semininingwane yakhiwa enezintambo, izimfanelo, futhi isendlalelo.
2. Ukuqopha - inombolo elibanzi imigqa ukuthi sibonise idatha agcwele into echazwe. Sezinombolo okufakiwe wenza ngokuzenzakalelayo uhlelo.
3. Isichasiso - Data libonisa amakholomu SUMMARY.
4. Field. Kuyinto ikholomu inhlangano. Inombolo yabo - ukubaluleka fixed isethwe lapho kudalwa noma ukuguqulwa etafuleni.

Manje, uma wazi ukuthi izakhi abamelwe kwetafula, ungakwazi udlulele izakhiwo zingubudlelwane imodeli semininingwane:

• Ingqikithi mgudumbili semininingwane zingubudlelwane. Ngenxa yalesi impahla nabo prodelyvat kalula imisebenzi ehlukahlukene ngekulandzelana zezibalo.
• I-oda lemfanelo amagugu kanye namarekhodi kuthebula zingubudlelwane kungaba ezingafanele.
• Ikholomu ngaphakathi itafula zingubudlelwane kumele babe igama layo siqu esiyingqayizivele.
• Yonke idatha kukholamu ngokuyisisekelo ube obuphelele esinqunyiwe kanye yohlobo olufanayo.
• Noma yimuphi entry empeleni kubhekwa njengento eyodwa ucezu idatha.
• izingxenye ababamele imigqa ahlukile. Imvelo zingubudlelwane Awekho imigqa impinda.

Ngokusekelwe izakhiwo database zingubudlelwane kuyaqondakala ukuthi amagugu yezimfanelo kufanele kube yohlobo olufanayo, ubude. Cabanga ethile ngemfanelo amagugu.

I izici eziyinhloko emasimini yolwazi zingubudlelwane

amagama Field kumele ahluke ngaphakathi yomkhakha owodwa. Nazi izinhlobo izimfanelo noma amasimu yolwazi zingubudlelwane ukuchaza isigaba idatha egcinwe emasimini inhlangano. Field semininingwane zingubudlelwane Kufanele ube usayizi esinqunyiwe, ebalwa e izinhlamvu. Amapharamitha nefomethi amagugu ngemfanelo ukuchaza ngendlela yokulungisa idatha yabo. Nokho kukhona into okuthiwa "imaski" noma "isifanekiso yokufaka". It yakhelwe ukunquma ukucushwa kwe-okokufaka idatha ku ukubaluleka ngemfanelo. Ngokuqinisekile ngesikhathi okungalungile irekhodi uhlobo idatha kufanele ikhishwe umbiko bug emkhakheni. Futhi enkundleni izakhi ezinye ukulinganiselwa - izimo ekubhekeni ukunemba nokunemba idatha entry. Kukhona saziso imfanelo eyigugu oyingqayizivele kufanele egcwele idatha. Ezinye umugqa ngemfanelo nigcwaliswe null-amagugu. Bavunyelwa ukuba bangene eZweni ezingenalutho izimfanelo idatha ensimini. Njenganoma umbiko bug, kukhona izinto ezibaluleke agcwaliswa ngokuzenzakalela uhlelo - lena yemininingwane emisiwe. Ukuze kusheshiswe sesha noma yimaphi idatha okuhloswe ensimini okukhonjiwe.

Isikimu ntathu ithebula semininingwane zingubudlelwane

Ukuze uthole ukuqonda ukwaziswa okuningiliziwe ngalesi ukuphathwa uhlelo imodeli usebenzisa SQL ngcono ukucabangela isikimu njengesibonelo. Sesiyazi ukuthi kuyinto database zingubudlelwane. An entry etafuleni ngalinye - a idatha ye-elementi eyodwa. Ukuvimbela idatha komsebenzi, kudingekile ukuba kulesetayelekile ukusebenza.

Imithetho eyisisekelo ukuzinza bemvelo zingubudlelwane

1. Inani igama inkambu itafula zingubudlelwane kumele ahluke, alifani nelamuntu (Okokuqala Jwayelekile Ifomu - 1NF).

2. Ukuze itafula osekuvele sehliselwe 1NF, okungezona ekukhombeni egameni lanoma imuphi ikholomu kungancika ekutholakaleni itafula esehlukile (2NF).

3. Ngoba wonke amatafula kakade egcinwe ku 2NF, okungezona ekukhombeni inkambu kungaba ezimele ezinye abangaziwa isici namanani (3NF inhlangano).

Yolwazi: izixhumanisi zingubudlelwane phakathi amatafula

Kukhona 2 main izinhlobo ubudlelwane amaphilisi zingubudlelwane:

• "Omunye-abaningi". Ngokusho kwenzeka uma izimo Ukhiye ithebula entry №1 eziningi inhlangano yesibili. isithonjana Key omunye kube semikhawulweni umugqa ungenisa ibonisa ukuthi ketshezi kuyinto ohlangothini "omunye", kube komunye umkhawulo emgqeni ngokuvamile iwuphawu infinity uphawu.

• Ukuxhumana "abaningi-abaningi" wawubumba endabeni imigqa eziningana eyodwa okunengqondo inhlangano nokuxhumana okubeka obala nge eziningana amarekhodi kwelinye itafula.
• Uma izinhlangano ezimbili kukhona concatenation ka "omunye komunye", kusho ukuthi isihlonzi ayisihluthulelo itafula elikhona elinye ibhizinisi, khona-ke kuyadingeka ukuze asuse omunye amatafula, akudingekile. Kodwa ngezinye izikhathi kuphela program ezokuphepha ngenhloso ukwehlukanisa izinhlangano ezimbili. Ngakho-ke, ngombandela, ukuxhumana phakathi "omunye komunye" angaba khona.

Ukuba khona okhiye database zingubudlelwane

okhiye zamabanga aphansi naphezulu nokubona izinto ezingase zibe semininingwane ubudlelwano. Zingubudlelwane zokuxhumana idatha imodeli ungaba ukhiye ikhandidethi kuphela eyodwa, kuyoba ukhiye oyihloko. Kuyini lokhu? ukhiye oyihloko - ikholomu noma iqoqo izimfanelo we okushiwo, lapho ungakwazi ukufinyelela othile umugqa idatha. Kufanele kube esiyingqayizivele, kuphela, nasemasimini alo ayikwazi ukuqukatha amagugu null. Uma ukhiye oyihloko siqukethe imfanelo eyodwa kuphela, khona-ke kuthiwa elula, ngaphandle kwalokho kuyoba.

Ngaphandle ukhiye oyihloko, likhona futhi yangaphandle (ukhiye angaphandle). Abaningi abakuqondi lokho mehluko phakathi kwabo. Ake sihlole ngokuningiliziwe njengesibonelo. Ngakho, kukhona amatafula amabili: "Dean" futhi "abafundi". Ingqikithi "Dean" liqukethe imikhakha: ". Iqembu" "i-ID umfundi", "Igama" futhi Ithebula "Abafundi" unamanani ngemfanelo ezifana "Igama", "Iqembu" futhi "Isilinganiso". Ngakho njengesixwayiso, ama-ID umfundi akukwazi ukuba abafundi abambalwa okufanayo, kuba emkhakheni kube ukhiye oyihloko. "Igama" futhi "Iqembu" kusukela "abafundi" kwetafula kungenzeka ukuba abantu abambalwa okufanayo, babhekisela inombolo ye-ID yomfundi kusuka ngokuyisisekelo "Dean", ngakho ingasetshenziswa njengendlela ukhiye angaphandle.

Isibonelo zingubudlelwane imodeli semininingwane

Ngokucaca, sikunikeza isibonelo okulula imodeli semininingwane zingubudlelwane ehlanganisa izinhlangano ezimbili. Kunetafula elinegama elithi "Dean".

Kuyadingeka ukuba afeze uxhumano ukuze uthole semininingwane egcwele zingubudlelwane. Ukungena "IN-41" kanye "IN-72", kungase kube khona izikhathi ezingaphezu kwesisodwa ethebuleni "Dean" njengoba nesibongo, igama patronymic abafundi, ezimweni ezingajwayelekile, kungaba okufanayo, ngakho kula masimu akukwazi ukwenza ukhiye oyihloko. ngokuyisisekelo ukuthi "abafundi" sizobonisa.

Njengoba singabona, izinhlobo zingubudlelwane semininingwane Amasimu kuhluke ngokuphelele. Yethula njengoba okuqoshiwe digital futhi uhlamvu. Ngakho-ke, izilungiselelo ngemfanelo kufanele bakhombise ukubaluleka inamba, Isakare, vachar, usuku kanye nabanye. Esikhathini "Dean" Inani unique ID umfundi kuphela. Le nkambu zingafundwa njengoba ukhiye eyinhloko. Igama, umculi, futhi ifoni kusuka ngokuyisisekelo ukuthi "abafundi" lingase lithathwe njengendlela ukhiye angaphandle esinereferensi ID umfundi. Uxhumano Kumiswa. Lena isibonelo imodeli zokuxhumana "omunye komunye". Ngombandela, omunye amatafula extra, bona zingahlanganiswa kalula yomkhakha owodwa. Ukuze i-ID-inani labafundi ayibanga emhlabeni eyaziwa, kungenzeka ukuthi kukhona amatafula amabili.