Database Relationships

Dhiyabhorosi hukama hutsva hwehuse hwekodzero dzekodzero

Ukama hunosimbiswa pakati pematafura maviri epa database apo imwe tafura ine chinyorwa chekune imwe nyika iyo inotaura chiyi chekutanga cheimwe tafura. Ichi ndicho chirevo chekutanga shure kwezwi re database database.

Kushandiswa Kwakaitwa Mutorwa Wekune imwe nyika Kuita Ushamwari

Ngatimbokurukurai nheyo dzemitemo yekutanga uye yekunze. Chinokosha chikuru chinonyanya kuzivisa zvinyorwa zvose mutafura. Icho chimiro chekutsvaga chinhu chinowanzova korona yekutanga mutafura uye inogona kuve yakangoerekana yakagadzirwa ned database kuitira kuti ione kuti yakasiyana.

Chiyi chekunze kune imwe nzvimbo yakakosha (kwete yekutanga inoshandiswa) yakashandiswa kubatanidza zvinyorwa kune data mune imwe tafura.

Semuenzaniso, funga mabhesi awa maviri anoratidza kuti mudzidzisi anodzidzisei nzira ipi.

Pano, dhesi yeChese yekutanga ndiyo Course_ID. Chiyi chayo chekune imwe nyika ndiWeacher_ID:

Iwe unogona kuona kuti kiyi yekunze muChikoro inofanidza chinhu chikuru paVadzidzisi:

Tinogona kutaura kuti Mudzidzisi_ID kecheni chekune dzimwe nyika yakabatsira kusimbisa ukama pakati peDzidzo uye matafura eVadzidzisi.

Mitauro yeDatabase Relationships

Kushandisa zvigere zvekune dzimwe nyika, kana zvimwe zvigaro zvekugadzirira, unogona kushandisa mitatu yehukama pakati pematafura:

Imwe-kune-imwe : Urudzi urwu hwehukama hunobvumira chete imwe rekodi kune rumwe rutivi rwehukama.

Chinokosha chikuru chinoratidzira nekodhi imwe chete-kana kuti isina - mune imwe tafura. Somuenzaniso, mumuchato, mumwe nemumwe ane mumwe mumwe chete. Urwu hukama hweukama hunogona kushandiswa mune imwe tafura uye naizvozvo haishandisi kiyi yekunze.

Mumwe-kune-vazhinji : Ukama humwe-kune-hwakawanda hunobvumira rekodhi imwe chete mune imwe tafura kuti ienderane nezvinyorwa zvakawanda mune imwe tafura.

Funga nezvebhizimisi rine database rakagadzirirwa nevatengi uye mazita ekuraira.

Mumwe mutengi anogona kutenga mitemo yakawanda, asi chirevo chimwe chete hachikwanisi kusanganiswa kune vatengi vakawanda. Nokudaro Dare reMitemo raizova nekona yekunze inofanana nekona yekutanga yeTerenda yevatengi, asi tafura yevatengi haizati iine imwe nyika yekunze inotsanangurira tafura yeAraders.

Vakawanda-kune-vazhinji : Iyi ishamwari yakaoma iyo yakawanda yakawanda iri mutafura inogona kuwirirana nezvinyorwa zvakawanda mune imwe tafura. Semuenzaniso, bhizimisi redu haringadi chete Vatengi uye maTereji ematafura, asi zvichida anodawo Mishonga patafura.

Zvakare, ukama huri pakati pevatengesi nemirairo yekurayira ndeye-kune-zhinji, asi funga ukama huri pakati peMitemo uye Zvimwe zvinhu. Murairo unogona kuva nemishonga yakawanda, uye chigadzirwa chingave chakabatanidzwa nemirairo yakawanda: vatengi vanoverengeka vanogona kutumira mutemo une zvimwe zvezvinhu zvakafanana. Iko rudzi rwehukama hunodiwa pamadanda matatu pasi.

Ndeipi Database Relationships Inokosha?

Kugadzirisa ukama hukama pakati pematafura ehurumende kunobatsira kuchengetedza kutendeseka kwemashoko, kugovera ku database yekusimudzira. Semuenzaniso, zvakadini kana isu tisina kubatanidza chero mahwendefa kuburikidza nekona yekunze uye pane kungobatanidza data mumatafura eRussia uye Mudzidzisi, zvakadai sekuti:

Izvi zvinogadziriswa uye zvinoputsa mutemo wekutanga wekodzero yepamusoro yepamusoro, Form First Form (1NF), iyo inotaura kuti rimwe nerimwe retafura rinofanira kuva neshoko rimwe chete, rakanyatsonaka re data.

Kana kuti zvimwe takasarudza kuwedzera kechipiri cheCarmen, kuitira kuti titsigire 1NF:

Ichi ichiri chisina kusimba, kuunza kudzokorora kusingadikanwi uye izvo zvinonzi kudhevedzwa kwemashoko anomalies , izvo zvinongoreva kuti zvinogona kuita kuti zvinhu zvisakanganise.

Somuenzaniso, kana mudzidzisi ane zvinyorwa zvakawanda, zvakadini kana mamwe mashoko achida kugadziriswa, asi munhu anoita kudhindwa kwezvinhu haazivi kuti zvinyorwa zvakawanda zviripo? Tafura yacho inogona kunge yakagadzirirwa dunhu rakasiyana, pasina nzira yakajeka yekuzviziva kana kuidzivisa.

Kuputsa tafura iyi mumatafura maviri, Teachers and Courses (sezvakaratidzwa pamusoro), inoita ukama hwakanaka pakati pe data uye naizvozvo inobatsira kuchengetedza ruzivo rwehutano nekururama.