He aha te Puka Whakanoho-Tae-Whawhai (BCNF)?

by Mike Chapple

Ko te BCNF te whakaiti i nga waahi me te whakapiki i te pono o te raraunga

Ko te whāinga o Boyce-Codd Normal Form (BCNF) ko te whakapiki ake i te tika o te raraunga ma te whakarite i nga pou me nga ripanga o te papanga raupapa whakawhiti mo te whakatutuki i te hanganga paerewa. Ka puta te hanganga pätengi raraunga ka whakauruhia he whanaungatanga i waenga i nga ripanga me te wa i tautuhia ai e nga ripanga nga ture kia pai ake ai te paerewa me te tiaki i nga raraunga.

Ko nga whāinga o te hanganga pātengi raraunga ko te whakakore i nga raraunga korerua me te whakarite i te tikanga o te whakawhirinaki raraunga.

Kei te raupapa te papaapuhi kaore e rawekehia nga raraunga ano i roto i te ripanga kotahi neke atu i te kotahi, me te waahi ka tohua nga raraunga e pa ana ki roto i te ripanga.

Ko te putanga o te Boyce-Codd Formal Form

I te whai i te raupapa o nga aratohu kia tino whakaritehia nga paparanga raraunga. Ko enei aratohu e kiia ana ko nga ahua noa me te nama mai i te kotahi ki te rima. Kei te whakaahuahia he pātengi raraunga whakawhitiwhitinga kia rite ki te hanganga mehemea ka tutuki ia i nga waahanga tuatahi e toru: 1NF, 2NF, me te 3NF.

I hangaia te BCNF hei whakatairanga ki te puka tuatoru, 3NF ranei, i te tau 1974 na Raymond Boyce me Edgar Codd. Kei te mahi nga tangata ki te hanga i nga papaahana raraunga e whakaiti ana i nga rereketanga me te whāinga o te whakaiti i te wa whakahaere. Ko te ahua tuatoru o te ahua e tango ana i nga pou e kore e whakawhirinaki ana ki te matua matua ki te whakatutuki i nga aratohu i roto i nga waahanga tuatahi me te tuarua. Ko te BCNF, e kiia ana ko te 3.5NF i etahi wa, e tutuki ana i nga whakaritenga katoa o te 3NF, me te hiahia kia kaua he paanga o nga taviri kaitono ki etahi atu huanga i roto i te ripanga.

I te wa i hangaia ai a BCNF, ko Boyce tetahi o nga kaihanga matua o te Reo Ingarihi Ingarihi (SQL), he pai ake te tango mai i te raraunga ma te whakamahi i te tauira whanaungatanga o Codd. I roto i tenei tauira, i kii a Codd ka taea te whakaiti i te uaua hanganga o nga raraunga, ko te tikanga ko nga uiuinga he kaha ake, hewari hoki.

Mā te whakamahi i ōna mōhiotanga pātengi raraunga, ko te tautuhinga Codd 1NF, 2NF, me te 3NF. I mahi tahi ia me Boyce hei tohu i te BCNF.

Ko nga kaitono me te BCNF

Ko te matua kaitono he tīwae, he huinga rānei o nga pou i roto i te ripanga e tuhi ana i te matua ahurei i roto i te pātengi raraunga. Ka taea te whakamahi i nga huanga ki te tautuhi i te papaunga raraunga kaore e korero ana ki etahi atu raraunga. Ka taea e ia tepu te whakauru i nga mahinga kaitono maha, ka taea e tetahi o enei te tohu hei matua matua. Kei te ripanga anake te matua matua tuatahi.

Ko nga taviri kaitono he mea motuhake.

Ko te whanaungatanga kei roto i te BCNF mēnā he kaitono kaitono te kaiwhakaatu katoa. Whakaarohia he ripanga pātengi raraunga e tiaki ana i nga korero a nga kaimahi me nga huanga , , , me te . </p> <p> I tenei tepu, ka tohu te mara <Employee_Id> te ingoa tuatahi me te ingoa whakamutunga. Waihoki, ko te tuple (<Tuatahi_name,, <Last_name>) ka whakatau <Employee_id>. </p> <table><tbody><tr><td> <strong>Ko te mahi kaimahi</strong> </td><td> <strong>Ingoa tuatahi</strong> </td><td> <strong>Ingoa whakamutunga</strong> </td><td> <strong>Taitara</strong> </td></tr><tr><td> 13133 </td><td> Emily </td><td> Smith </td><td> Kaiwhakahaere </td></tr><tr><td> 13134 </td><td> Jim </td><td> Smith </td><td> Hoa </td></tr><tr><td> 13135 </td><td> Emily </td><td> Jones </td><td> Hoa </td></tr></tbody></table><p><br> Ko te matua kaitono mo tenei <a href="https://mi.eyewated.com/te-papakupu-o-nga-paerewa-paerewa-raraunga/">paerewa</a> ko te <Employee_Id> no te mea ko te uara anake e kore e taea te whakamahi i tetahi atu rarangi. </p> </div> <div class="amp-related-wrapper"> <h2>Alike posts</h2> <div class="amp-related-content"> <a href="https://mi.eyewated.com/te-whakatakoto-i-tetahi-paerewa-i-te-puka-toa-tuatoru-3nf/"> <amp-img 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