Database zonxulumelwano. Ingqiqo ledatha zonxulumelwano

Ukuvela kobuchwepheshe computer kwiinkcukacha mihla kwaphawula revolution kuzo zonke iinkalo zezinto ezenziwa luluntu. Kodwa ngaba kuzo zonke ulwazi angabi inkunkuma okungeyomfuneko Internet, yaqanjwa kwinkqubo database, apho izinto ezibekwe, systematized, kunye result ukuba kulula ukufumana zize zingenise processing olulandelayo. Kukho iintlobo ezintathu eziphambili - allocating ezinobume database, oluneqela elinegunya, network.

uhle ezisisiseko

Ukubuyela kule ukuvela iinkcukacha, kufuneka kunokuthiwa inkqubo kakhulu entsonkothileyo, oko luphuma uphuhliso izixhobo inkcazelo processing ehlelwe. Ngoko ayimangalisi into yokuba inani imifuziselo ngoku ifikelela ngaphezu kwama-50, kodwa ezona ziphambili zithathwa oluneqela elinegunya, ezinobume kunye womnatha, nto leyo isasetyenziswa nangoku kakhulu practice. Yintoni abamele?

database oluneqela uba kwisakhiwo somthi yaye ubunjwe data kumanqanaba ahlukeneyo phakathi apho kukho unxibelelwano. imodeli database Network ngumzekelo nzima ngakumbi. nesakhiwo sayo, kufana zabefundisi, nesigqibo seengcinga kwandiswa kwaye ziphuculwe. Umahluko phakathi kwabo kukuba yemifanekiso data oluneqela ilifa kunokunxulunyaniswa kunye izinyanya omnye kuphela, lo gama womnatha inokuba ezininzi. Enjengesakhiwo zonxulumelwano database unzima kakhulu ngakumbi. Ngoko ke, kufuneka lidilizwe banzi.

Ingcamango olusisiseko database zonxulumelwano

Le modeli waphuhliswa ngo-1970 nguGqirha Edgar F. Codd inzululwazi. It is a itafile ngokusengqiqweni sakhiwe kunye namasimi ezichaza data, ubudlelwane phakathi kwabo nabanye, imisebenzi eyenziwa phezu kwabo, kwaye okona kubalulekileyo - nemithetho siqinisekiso ingqibelelo yabo. Kutheni le nto ibizwa ngokuba imodeli ezinobume? Oku kusekelwe ubudlelwane (ukusuka kwisiLatini. Relatio) phakathi data. Kukho iinkcazo ezininzi olu hlobo ledatha. neetafile zonxulumelwano ngolwazi kulula kakhulu ukuba amalungiselelo nokunika unyango, kunokuba uthungelwano okanye umfuziselo oluneqela elinegunya. Njani loo nto? Kwanele ukuba ukwazi iimpawu, isakhiwo imodeli neempawu tafile ezinobume.

Inkqubo yokubumba kunye ezisisiseko izinto

Ukwenzela ukwakha uvimba yakho, kufuneka usebenzise enye izixhobo yokubumba ukuze ukucinga oko inkcazelo oyifunayo ukusebenza, ukuyila itafile zonxulumelwano neelinki abangatshatanga kunye ezininzi phakathi kwezigqeba data ukuba bazalise le iseli uze usete izitshixo zaseprayimari okanye kwamanye amazwe.

Aphila iitafile kunye nokuyila zolwazi zonxulumelwano lwenziwa ngokusebenzisa izixhobo okhululekileyo njengathi Workbench, PhpMyAdmin, iTyala Studio, dbForge Studio. Emva ukudizayina oluneenkcukacha ukugcina imodeli graphic igqityiwe zonxulumelwano nesiguqulela ube SQL-olulungilyo lwe khowudi. Kweli nqanaba, ungaqalisa ukusebenza ukuhlela data, ukusetyenzwa systematization.

Iimpawu ngesakhiwo ngokoMthetho ezinxulumene imodeli ezinobume

umthombo ngamnye ngendlela yaso ichaza izinto zayo, ndingathanda kunika uthsuphe wokuba kangako isiphithiphithi ngaphantsi njalo:

• yokurekhoda ezinobume = nemvelo;
• layout = igama lophawu = igalufa = iqumrhu column ephepheni;
• iqumrhu Ngokomzekelo = tuple = irekhodi = umgca ipleyiti;
• sophawu = value = amaziko cell entsimini.

Ukuya ku iipropati sedata zonxulumelwano kufuneka bazazi ezinye ngeekhomponenti asisiseko iquka kwaye apho ke zenzelwe.

1. Umongo. Table database zonxulumelwano abe mnye, okanye inokuba iseti iitafile okuluphawu echazwe izinto zigcinwa khona nge i data. Bathi inani eliqingqiweyo amasimi, kwaye inani variable yezicelo. Table database imodeli zonxulumelwano ubunjwe strings, iimpawu, kunye nobeko.
2. Ukurekhoda - inani eziguquguqukayo lemiqolo ukuba ukubonisa idatha isenza into echazwe. Ababaliweyo entries wenza ngokuzenzekelayo yi le nkqubo.
3. Iimpawu - Data esibonakalise nezintlu ISISHWANKATHELO.
4. Field. Lo column entity. Inani labo - ixabiso esisigxina icwangcisiwe ngexesha indalo okanye ukuguqulwa kwetafile.

Ke kaloku, esazi izinto usemthethweni kwetafile, ungasa kwi iimpawu ledatha imodeli ezinobume:

• Isiseko sedata okuntlandlo-mbini zonxulumelwano. Ngenxa kule propati nabo ngokulula prodelyvat imisebenzi eyahlukeneyo ubhalo kunye zemathematika.
• Umyalelo lwamaxabiso lesiphumo neerekhodi unabo zonxulumelwano kunokuba ngokwesigqibo esicalanye.
• Column ngaphakathi kwetafile zonxulumelwano kufuneka negama layo eyahlukileyo.
• Yonke idatha kwikholam akuguquki babe ubude esisigxina kunye nohlobo olufanayo.
• Nayiphi na inguqu ithathwa njengenye iqhekeza ledata.
• amacandelo usemthethweni kweengcamba ezikhethekileyo. Uhlobo zonxulumelwano Akukho imiqolo phindo.

Ngokusekelwe iimpawu ledatha ezinobume, kuyaqondakala ukuba amaxabiso iimpawu kufuneka zibe ngohlobo olufanayo, ubude. Cinga amaxabiso ethile sophawu.

Eyona engundoqo iimpawu ingentsimi zolwazi zonxulumelwano

Amagama Field kufuneka ibe yodwa phakathi njengequmrhu elinye. Iindidi iimpawu okanye namasimi zolwazi zonxulumelwano ichaza udidi data egcinwe emasimini kwiqumrhu. Field database zonxulumelwano kufuneka abe ubukhulu bayo, ebalwayo ngoonobumba. Parameters kwaye ukufomata amaxabiso attribute zichaza indlela yokulungisa idatha yazo. Kodwa kukho into enje njenge "isigqumathelo" okanye "ithempleyithi igalelo". Iyilelwe ukuba ukujonga uqwalaselo input data kwi ixabiso ngemfanelo. Ngokuqinisekileyo irekhodi ephosakeleyo uhlobo data kufuneka ekhutshwe ingxelo yegciwane entsimini. Kwakhona endle iziqalelo ezinye iintsilelo - iimeko zokutshekisha nokuchaneka kunye ngqo zokufaka idatha. Kukho ixabiso attribute mandatory ababonisa ngokukhethekileyo kufuneka azaliswe data. Abanye umgca attribute ukuze ndizaliswe byte-values. Bavunyelwe ukuba bangene iimpawu Ifildi yeengcombolo engenanto. Njengokuba ingxelo yolungiso lweengxaki, kukho amaxabiso bazaliswe ngokuzenzekelayo yi-nkqubo - oku ke yeenkcukacha emiselweyo. Ukuze ukukhawulezisa ukufuna ukuba naziphi na iinkcukacha ekujongwe intsimi indexwa.

Scheme ntathu zonxulumelwano itheyibhile database

Ukuze ufumane ulwazi oluneenkcukacha inkqubo yolawulo imodeli usebenzisa SQL okusemandleni ukuqwalasela inkqubo njengomzekelo. Thina sele uyazi into database zonxulumelwano. Ungeno kwi table nganye - element data enye. Ukuthintela komsebenzi data, kuyimfuneko ukuba ukubuyisela ukusebenza.

Imithetho ezisisiseko kuqheleke uhlobo zonxulumelwano

1. Ixabiso igama nentsimi, ukuba ube itafile zonxulumelwano kufuneka ibe yodwa, omnye uhlobo (First Normal Form - 1NF).

2. Kuba yitafile sele lancipha ukuya 1NF, non-ukubona igama nawuphi na umqolo ukuba abaxhomekeke kwetafile isazisi esisodwa (2NF).

3. Kuba zonke iitafile ukuba sele zigcinwa 2NF, ezingezo-ukuchonga endle ngalinye kunokuba bazimele geqe namanye amaxabiso element abangaziwayo (3NF entity).

Edatha: amakhonkco zonxulumelwano phakathi iitafile

Kukho 2 eziphambili iintlobo lobudlelwane amacwecwe zonxulumelwano:

• "Omnye-ezininzi". Ngokutsho kwenzeka xa iimeko omnye wokungena itheyibhile №1 ezininzi yequmrhu yesibini. icon Key kwenye iziphelo kumgca azotywe ibonisa ukuba iziyobisi ophezu ecaleni "omnye", kwelinye icala selayini badla uphawu amanqaku obungapheliyo.

• Unxibelelwano "zininzi abaninzi 'kwasekwa kwimeko lemiqolo eziliqela eyodwa kuphela enengqondo iqumrhu intsebenziswano ecacileyo kunye nenani iingxelo kwenye itafile.
• Ukuba ezikhoyo ezimbini kukho concatenation of "enye ukuya kwenye", oko kuthetha ukuba isazisi ephambili kwetafile ekhoyo kwezinye iqumrhu, ngoko kuyimfuneko ukuba asuse enye iitafile, akufuneki. Kodwa ngamanye amaxesha kuphela badwelisi benkqubo yokhuseleko bazahlule ngabom magama mabini. Ngoko ke, ngombandela, unako khona uqhagamshelwano phakathi "enye ukuya kwenye".

Ubukho izitshixo kwidathabheyisi zonxulumelwano

izitshixo eziziiprayimari neziziisekondari ukuchonga ubudlelwane database enokwenzeka. imodeli nonxibelelwano data zonxulumelwano unokuba iqhosha ngumviwa enye kuphela, iya kuba iqhosha. Yintoni na? iqhosha Primary - ikholam okanye iseti iimpawu ubunjalo, apho unako ukufikelela umgca data ethile. Kufuneka ibe yodwa, kuphela, namasimi yayo ayikwazi ukugcina amaxabiso null. Ukuba iqhosha ibandakanya uphawu omnye kuphela, ngoko ke kuthiwa elula, kungenjalo kuya kubakho.

Ngaphandle iqhosha, likhona kwaye (iqhosha langaphandle) lwangaphandle. Abantu abaninzi abayiqondi into umahluko phakathi kwabo. Makhe sihlolisise ngokweenkcukacha ezingakumbi umzekelo. Ngoko ke, kukho iitafile ezimbini: "uDean" yaye "abafundi". Umongo "uDean" iqulethe amasimi: ". Group" "ID yomfundi", "Igama" yaye Uluhlu "Abafundi" liye amaxabiso lesiphumo ezifana "Igama", "Group" yaye "avareji". ngeke ibe okufanayo ngabafundi abambalwa kangaka ID umfundi, oko endle kuba iqhosha. "Igama" yaye "Group 'ukusuka' bafundi 'of the table isenokuba okufanayo abantu abambalwa, kubhekisela kwinani ID yomfundi ukususela umongo" Dean ", ngoko ke zingasetyenziswa njenge iqhosha langaphandle.

Umzekelo uReeva database zonxulumelwano

Ecacileyo, sinikela umzekelo elula kwemodeli ledatha zonxulumelwano ezibandakanya ezikhoyo ezimbini. Kukho itafile enegama "Dean".

Kuyimfuneko ukuphumeza uqhagamshelwano ukuze ufumane uvimba ngokupheleleyo zonxulumelwano. Iphetshana "IN-41" kunye "IN-72", kusenokuba kakhulu ngoku ngaphezu kanye itafile "uDean" njengoko ifani, igama patronymic abafundi, kwiimeko ezinqabileyo, unokuba efanayo, ngoko ke akuyi kubakho ezi amasimi ukuze ukwenza iqhosha. umongo "Abafundi" iya kubonisa.

Njengoko ubona, iintlobo amasimi sedata zonxulumelwano zahluke ngokupheleleyo. Inkcaza orekhodiweyo lwedijithali kunye nesimilo. Ngoko ke, lo izicwangciso attribute kufuneka zibonise ixabiso elipheleleyo, Isakare, vachar, umhla kunye nabanye. Xa "Dean" ixabiso eyahlukileyo i ID umfundi kuphela. Le intsimi singathathwa njenge iqhosha. Igama, igcisa, yaye ifowuni evela umongo "Abafundi" singathathwa njenge iqhosha langaphandle isalathisi le ID zomfundi. Kokuba uxhulumaniso lusekiwe. Lo ngumzekelo kwemodeli yonxibelelwano "enye ukuya kwenye". Ngombandela, omnye iitafile extra, ukuba kube lula kuhlanganiswa abe licandelo elinye. To le ID-inani labafundi abazange babe kwaziwa jikelele, kusenokwenzeka ukuba kukho iitafile ezimbini.