Multivalued Dependency mu Database Design

Kugonjera kwakukulu kumapangidwe kachitidwe kachitidwe kachinayi

Mu deta yolumikizana, kugonjera kumapezeka pamene mfundo zomwe zili mu deta imodzimodziyo zimapangitsanso zowonjezera zina zomwe zili mu tebulo lomwelo. Kudalira kwakukulu kumachitika pamene kukhalapo kwa mzere umodzi kapena kuposera patebulo kumatanthauza kupezeka kwa mzere umodzi kapena mizere mu tebulo lomwelo. Ikani njira ina, zizindikiro ziwiri (kapena zikho) mu tebulo zimadziimira okhaokha, koma zonse zimadalira chikhumbo chachitatu.

Kudalira kwakukulu kumathandiza kuti chikhalidwe chachinayi chikhale chachibadwa (4NF). Mafotokozedwe amtunduwu amatsatira mitundu isanu yachibadwa yomwe imayimira ndondomeko za zojambula. Amapewa zolakwika zosintha ndi zosagwirizana m'ma data. Fomu yachinayi yachibadwa imagwirizana ndi maubwenzi ambiri ku deta .

Ntchito yogwira ntchito ndi Multivalued Dependency

Kuti mumvetsetse kudalira kwakukulu, ndizothandiza kubwereranso momwe kudalira kumagwirira ntchito.

Ngati chidziwitso X chimapangitsa kuti Y, ndiye Y imadalira kwambiri X. Izi zinalembedwa ngati X -> Y. Mwachitsanzo, mwa Ophunzira pansipa, wophunzira_Name amadziwitsa akulu:

Kugonjera kotereku kungathe kulembedwa: Wophunzira_Name -> Wamkulu . Wophunzira aliyense_Name amatsimikiza chimodzimodzi Mmodzi, ndipo palibe.

Ngati mukufuna kuti deta iwonetsenso masewerawa ophunzirawo, mungaganize kuti njira yosavuta yochitira izi ndi kungowonjezera mzere wina wotchedwa Sport:

Vuto ili ndi lakuti Ravi ndi Bet amakonda kusewera masewera ambiri. Ndikofunika kuwonjezera mzere watsopano pa masewera ena onse.

Gome ili lapangitsa kuti anthu azidalira kwambiri chifukwa chachikulu ndi masewerawa ndi odziimira okhaokha koma zonse zimadalira wophunzirayo.

Ichi ndi chitsanzo chosavuta komanso chodziwikiratu mosavuta, koma kuvomereza kwa multivalue kungakhale vuto m'machinsinsi aakulu, ovuta.

Kudalira kwakukulu kwambiri kunalembedwa X -> -> Y. Pankhani iyi:

Student_Name -> -> Yaikulu
Student_Name -> -> Sport

Izi zimawerengedwa ngati "Wophunzira_Name Multidetermines Major" ndi "Student_Name multidetermines Sport."

Udindo wodalirika nthawi zonse umakhala ndi zikhumbo zitatu chifukwa zimakhala ndi zigawo ziwiri zomwe zimadalira gawo lachitatu.

Multivalued Dependency ndi Normalization

Gome lokhala ndi chidaliro chochuluka kwambiri limaphwanya miyezo ya normalization ya Fomu Yachibadwa Yachinayi (4NK) chifukwa imapanga zofunikira zosafunikira komanso zingapangitse deta yosagwirizana. Kuti mubweretse izi ku 4NF, m'pofunikira kuswa mfundoyi mu matebulo awiri.

Tebulo ili m'munsiyi liri ndi kudalira kogwira mtima kwa Ophunzira - Omwe -> Okuluakulu, ndipo palibe zokhudzana ndizinthu:

Ngakhale tebulo ili liri ndi ntchito imodzi yokha ya Ophunzira_Name -> Masewera:

Zikuwoneka kuti chizoloŵezi chimayesedwa mwa kuphweka matebulo ovuta kotero kuti ali ndi mauthenga okhudzana ndi lingaliro limodzi kapena mutu m'malo moyesera kupanga tebulo limodzi liri ndi zambiri zopanda pake.