Dè a th 'ann an Foirm àbhaisteach Boyce-Codd (BCNF)?

by Mike Chapple

Bidh BCNF a 'lùghdachadh nan dreuchdan às aonais agus a' meudachadh ionracas dàta

Is e an t-amas aig Foirm àbhaisteach Boyce-Codd (BCNF) meudachadh dàta a mheudachadh le bhith ag eagrachadh nan colbhan agus na clàran de stòr-dàta co-cheangailte gus normalachadh stòr-dàta a choileanadh. Bidh normalachadh bun-dàta a ' tachairt nuair a tha dàimhean stèidhichte eadar clàran agus cuin a tha riaghailtean mìneachaidh aig na clàran gus an stòr-dàta a dhèanamh nas sùbailte agus an dàta a ghleidheadh.

Is e na h-amasan aig gnàthachadh an stòr-dàta cur às do dhàta nach eil feumach agus gus dèanamh cinnteach gu bheil earbsaidhean dàta a 'dèanamh ciall.

Tha stòr-dàta àbhaisteach nuair nach eil an aon dàta air a stòradh ann an barrachd air aon chlàr agus nuair nach eil ach dàta co-cheangailte air a stòradh ann an clàr.

Tùs Foirm àbhaisteach Boyce-Codd

A 'leantainn sreath de stiùiridhean dèanamh cinnteach gu bheil stòran-dàta àbhaisteach. Thathas a 'toirt iomradh air an stiùireadh seo mar fhoirmean àbhaisteach agus tha iad air an àireamhachadh bho aon gu còig. Tha stòr-dàta co-cheangailte air a mhìneachadh mar as àbhaist ma choileas e ris a 'chiad trì foirmean: 1NF, 2NF, agus 3NF.

Chaidh BCNF a chruthachadh mar leudachadh air an treas foirm àbhaisteach, no 3NF, ann an 1974 le Raymond Boyce agus Edgar Codd. Bha na fir ag obair gus sgeamaichean stòr-dàta a chruthachadh a bha a 'dèanamh uiread de dhreuchdan a dh' ionnsaigh an amas a bhith a 'lùghdachadh ùine coimpiutair. Bidh an treas foirm àbhaisteach a 'toirt às do cholbhan nach eil an crochadh air a' phrìomh bhunait a thuilleadh air a bhith a 'coinneachadh ris an stiùireadh anns a' chiad agus an dàrna foirm àbhaisteach. BCNF, a tha air ainmeachadh mar 3.5NF uaireannan, a 'coinneachadh ri riatanasan 3NF agus a' cur feum air na h-iuchraichean tagraiche nach eil eisimeileachd sam bith air feartan eile ann am bòrd.

Aig àm cruthachadh BCNF, bha Boyce air aon de na prìomh luchd-leasachaidh air Cànan Ceist Structured English (SQL), a bha a 'leasachadh dàta air ais tro bhith a' cleachdadh modal dàimh Codd. Anns a 'mhodal seo, chomharraich Codd gum faodadh iom-fhillteachd structarail stòran-dàta a bhith air a lùghdachadh, rud a bha a' ciallachadh gum faodadh ceistean a bhith nas cumhachdaiche agus sùbailte.

A 'cleachdadh lèirsinnean an dàta co-cheangailte ris, tha Codd a' mìneachadh 1NF, 2NF, agus 3NF stiùireadh. Thàinig e còmhla ri Boyce gus BCNF a mhìneachadh.

Clabhairean Tagraiche agus BCNF

Is e colbh no measgachadh de cholbhan ann an clàr a th 'ann an iuchair tagraiche a tha na phrìomh uidheam anns an stòr-dàta. Faodar am measgachadh de bhuadhan a chleachdadh gus clàr stòr-dàta a chomharrachadh gun a bhith a 'toirt iomradh air dàta sam bith eile. Faodaidh grunn iuchraichean tagraiche a bhith anns gach clàr, agus faodaidh aon dhiubh a bhith freagarrach mar phrìomh iuchair. Chan eil ach aon phrìomh phrìomh chlàr ann an clàr.

Feumaidh iuchraichean tagraiche a bhith air leth.

Tha dàimh ann an BCNF ma tha a h-uile neach-tomhais na phrìomh thagraiche. Beachdaich air clàr stòr-dàta a tha a 'stòradh fiosrachadh luchd-obrach agus a bheil na buadhan , , , and . </p> <p> Anns a 'bhòrd seo, tha an achadh <Employee_Id> a' dearbhadh a 'chiad ainm agus an t-ainm mu dheireadh. San aon dòigh, tha an tuple (<First_name>, <Last_name>) a 'co-dhùnadh <Employee_id>. </p> <table><tbody><tr><td> <strong>Luchd-obrach Id</strong> </td><td> <strong>A’ chiad ainm</strong> </td><td> <strong>An t-ainm mu dheireadh</strong> </td><td> <strong>Tiotal</strong> </td></tr><tr><td> 13133 </td><td> Emily </td><td> Smith </td><td> Manaidsear </td></tr><tr><td> 13134 </td><td> Seumas </td><td> Smith </td><td> Com-pàirtiche </td></tr><tr><td> 13135 </td><td> Emily </td><td> Jones </td><td> Com-pàirtiche </td></tr></tbody></table><p><br> Is e an iuchair tagraiche airson an <a href="https://gd.eyewated.com/beag-fhaclair-de-chumhachan-coitcheann-an-stor-data/">stòr-dàta</a> seo an <Employee_Id> oir is e an aon luach nach urrainn a chleachdadh le sreath eile. </p> </div> <div class="amp-related-wrapper"> <h2>Alike posts</h2> <div class="amp-related-content"> <a href="https://gd.eyewated.com/dileasachd-gniomhach-ann-an-stor-data/"> <amp-img src="https://exse.eyewated.com/pict/50bf3b3f91fc2f54-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/dileasachd-gniomhach-ann-an-stor-data/">Dìleasachd Gnìomhach ann an Stòr-dàta</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/a-staladh-freiceadan-sql-2014-deasachadh-express/"> <amp-img src="https://exse.eyewated.com/pict/f54f603092813669-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/a-staladh-freiceadan-sql-2014-deasachadh-express/">A 'Stàladh Freiceadan SQL 2014 Deasachadh Express</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/a-staladh-mysql-air-mac-os-x-10-7-leomhann/"> <amp-img src="https://exse.eyewated.com/pict/58bb0e18465533f8-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/a-staladh-mysql-air-mac-os-x-10-7-leomhann/">A 'stàladh MySQL air Mac OS X 10.7 Leòmhann</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/de-a-th-ann-an-iuchair-bun-sgoile/"> <amp-img src="https://exse.eyewated.com/pict/b80e559b01543395-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/de-a-th-ann-an-iuchair-bun-sgoile/">Dè a th 'ann an iuchair bun-sgoile?</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/na-tha-a-dhith-ort-mu-chanan-ceist-steidhichte/"> <amp-img src="https://exse.eyewated.com/pict/56d5a9252fd2424e-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/na-tha-a-dhith-ort-mu-chanan-ceist-steidhichte/">Na tha a dhìth ort mu chànan ceist stèidhichte</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/stor-data-samplach-microsoft-access-2007/"> <amp-img src="https://exse.eyewated.com/pict/829ebd6ab9902fde-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/stor-data-samplach-microsoft-access-2007/">Stòr-dàta Samplach Microsoft Access 2007</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/doighean-obrach-air-an-storadh/"> <amp-img src="https://exse.eyewated.com/pict/b5acd1c1e5392fac-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/doighean-obrach-air-an-storadh/">Dòighean-obrach air an stòradh</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/a-cleachdadh-microsoft-access-sa-ghniomhachas-beaga-agad/"> <amp-img src="https://exse.eyewated.com/pict/bfa74b601352305f-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/a-cleachdadh-microsoft-access-sa-ghniomhachas-beaga-agad/">A 'cleachdadh Microsoft Access sa Ghnìomhachas Beaga agad</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/cuairt-access-2013-an-eadar-aghaidh-cleachdaiche/"> <amp-img src="https://exse.eyewated.com/pict/2010a47098b93080-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/cuairt-access-2013-an-eadar-aghaidh-cleachdaiche/">Cuairt Access 2013: An Eadar-aghaidh Cleachdaiche</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> </div> <div class="amp-related-wrapper"> <h2>See Newest</h2> <div class="amp-related-content"> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/na-8-headphones-jbl-as-fhearr-ri-ceannach-ann-an-2018/">Na 8 Headphones JBL as Fheàrr ri Ceannach ann an 2018</a></h3> <div class="amp-related-meta"> A 'ceannach treòrachadh </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/laraich-lin-as-fhearr-guilty-as-fhearr/"> <amp-img src="https://exse.eyewated.com/pict/a5bf460c0d8f358f-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/laraich-lin-as-fhearr-guilty-as-fhearr/">Làraich-lìn as Fheàrr Guilty as Fheàrr</a></h3> <div class="amp-related-meta"> Lìn & lorg </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/suidhich-air-buidhnean-airson-postadh-ann-am-post-aim-agus-post-aol/"> <amp-img src="https://exse.eyewated.com/pict/5724da3bab30474a-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/suidhich-air-buidhnean-airson-postadh-ann-am-post-aim-agus-post-aol/">Suidhich air Buidhnean airson Postadh ann am Post AIM agus Post AOL</a></h3> <div class="amp-related-meta"> Post-d agus teachdaireachd </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/mar-a-chruthaicheas-tu-raointean-lin-ueir/"> <amp-img src="https://exse.eyewated.com/pict/a651eea500883185-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/mar-a-chruthaicheas-tu-raointean-lin-ueir/">Mar a chruthaicheas tu raointean-lìn uèir</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/mar-a-chuireas-tu-a-steach-faidhlichean-calendair-ics/"> <amp-img src="https://exse.eyewated.com/pict/574b440603024596-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/mar-a-chuireas-tu-a-steach-faidhlichean-calendair-ics/">Mar a chuireas tu a-steach Faidhlichean Calendair ICS</a></h3> <div class="amp-related-meta"> Post-d agus teachdaireachd </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/na-dhfheumas-tu-fios-a-bhith-agad-gus-iphone-a-ipad-a-shonrachadh/"> <amp-img src="https://exse.eyewated.com/pict/2abb6b0ab2bb3466-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/na-dhfheumas-tu-fios-a-bhith-agad-gus-iphone-a-ipad-a-shonrachadh/">Na dh'fheumas tu fios a bhith agad gus iPhone a iPad a shònrachadh</a></h3> <div class="amp-related-meta"> IPhone & iPod </div> </div> </div> </div> <div class="amp-related-wrapper"> <h2>Sapid posts</h2> <div class="amp-related-content"> <a href="https://gd.eyewated.com/mar-a-gheibh-thu-an-asgaidh-cairtean-tiodhlac-xbox-ms-points/"> <amp-img src="https://exse.eyewated.com/pict/930f5db2e28232bf-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/mar-a-gheibh-thu-an-asgaidh-cairtean-tiodhlac-xbox-ms-points/">Mar a gheibh thu an-asgaidh Cairtean Tiodhlac Xbox (MS Points)</a></h3> <div class="amp-related-meta"> Gaming </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/mar-a-chosgas-tu-notaichean-coise-agus-notaichean-ann-an-word-2010/"> <amp-img src="https://exse.eyewated.com/pict/a47625abac9b2ec7-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/mar-a-chosgas-tu-notaichean-coise-agus-notaichean-ann-an-word-2010/">Mar a chosgas tu notaichean-coise agus notaichean ann an Word 2010</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/sgrudadh-moana/"> <amp-img src="https://exse.eyewated.com/pict/6e407e735bcd379e-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/sgrudadh-moana/">Sgrùdadh Moana</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/ces-2014-fonaichean-fuaim-ura/"> <amp-img src="https://exse.eyewated.com/pict/2a21758be87e2fa2-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/ces-2014-fonaichean-fuaim-ura/">CES 2014: Fònaichean-fuaim ùra</a></h3> <div class="amp-related-meta"> A 'ceannach treòrachadh </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/luchd-labhairt-leabhraichean-air-leth-agus-de-a-tha-ceart-dhut/"> <amp-img src="https://exse.eyewated.com/pict/af89ba8f38c938a0-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/luchd-labhairt-leabhraichean-air-leth-agus-de-a-tha-ceart-dhut/">Luchd-labhairt leabhraichean air leth agus dè a tha ceart dhut?</a></h3> <div class="amp-related-meta"> Theatre Dachaigh </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/camcorders-buidseit-as-fhearr/"> <amp-img src="https://exse.eyewated.com/pict/4e7cb35a2c73366b-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/camcorders-buidseit-as-fhearr/">Camcorders Buidseit as Fheàrr</a></h3> <div class="amp-related-meta"> A 'ceannach treòrachadh </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/de-a-th-ann-an-faidhle-flv/"> <amp-img src="https://exse.eyewated.com/pict/c0a5652225593172-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/de-a-th-ann-an-faidhle-flv/">Dè a th 'ann an faidhle FLV?</a></h3> <div class="amp-related-meta"> Windows </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/bunaitean-ailtireachd/"> <amp-img src="https://exse.eyewated.com/pict/7641a188fa413163-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/bunaitean-ailtireachd/">Bunaitean Ailtireachd</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/na-7-beanies-bluetooth-as-fhearr-ri-cheannach-ann-an-2018/">Na 7 Beanies Bluetooth as Fheàrr ri cheannach ann an 2018</a></h3> <div class="amp-related-meta"> A 'ceannach treòrachadh </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/cruthaich-no-ath-chomharran-aiseagan-meur-chlar-ann-an-microsoft-office/"> <amp-img src="https://exse.eyewated.com/pict/383b9e8d186f3320-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/cruthaich-no-ath-chomharran-aiseagan-meur-chlar-ann-an-microsoft-office/">Cruthaich no ath-chomharran Aiseagan-meur-chlàr ann an Microsoft Office</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> <div class="amp-related-content"> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/na-10-geamaichean-pc-ro-innleachd-as-fhearr-as-fhearr-ann-an-2018/">Na 10 Geamaichean PC Ro-innleachd as Fheàrr as Fheàrr ann an 2018</a></h3> <div class="amp-related-meta"> A 'ceannach treòrachadh </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/a-sgriobhadh-html-ann-an-notepad/"> <amp-img src="https://exse.eyewated.com/pict/2fb0aeb59c9a33d5-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/a-sgriobhadh-html-ann-an-notepad/">A 'sgrìobhadh HTML ann an Notepad</a></h3> <div class="amp-related-meta"> Dealbhadh Lìn & Deasg </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/na-h-eacarsaich-top-9-laraichean-airson-an-asgaidh/"> <amp-img src="https://exse.eyewated.com/pict/3455f7a8e04f34b0-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/na-h-eacarsaich-top-9-laraichean-airson-an-asgaidh/">Na h-eacarsaich Top 9 Làraichean airson an-asgaidh</a></h3> <div class="amp-related-meta"> Lìn & lorg </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/eachdraidh-nan-geamannan-bhidio-classic-aois-discovery/"> <amp-img src="https://exse.eyewated.com/pict/45a5760da7ef32b9-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/eachdraidh-nan-geamannan-bhidio-classic-aois-discovery/">Eachdraidh nan Geamannan Bhidio Classic - Aois Discovery</a></h3> <div class="amp-related-meta"> Gaming </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/faigh-stiuiridhean-coiseachd-le-google-maps/"> <amp-img src="https://exse.eyewated.com/pict/d647bab533e13574-120x86.png" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/faigh-stiuiridhean-coiseachd-le-google-maps/">Faigh stiùiridhean coiseachd le Google Maps</a></h3> <div class="amp-related-meta"> Android </div> </div> </div> <div class="amp-related-content"> <a href="https://gd.eyewated.com/rud-as-fhearr-as-fhearr-le-bathar-bog-foillseachaidh-deasg/"> <amp-img src="https://exse.eyewated.com/pict/e1ca1104b4e43466-120x86.jpg" width="120" height="86" layout="responsive" class="amp-related-image"></amp-img> </a> <div class="amp-related-text"> <h3><a href="https://gd.eyewated.com/rud-as-fhearr-as-fhearr-le-bathar-bog-foillseachaidh-deasg/">Rud as Fheàrr as Fheàrr Le Bathar-bog Foillseachaidh Deasg</a></h3> <div class="amp-related-meta"> Bathar-bog </div> </div> </div> </div></article> <footer class="amp-wp-footer"> <div class="amp-wp-footer-inner"> <a href="#" class="back-to-top">Back to top</a> <p class="copyright"> © 2024 gd.eyewated.com </p> <div class="amp-wp-social-footer"> <a href="#" class="jeg_facebook"><i class="fa fa-facebook"></i> </a><a href="#" class="jeg_twitter"><i class="fa fa-twitter"></i> </a><a href="#" class="jeg_google-plus"><i class="fa fa-google-plus"></i> </a><a href="#" class="jeg_pinterest"><i class="fa fa-pinterest"></i> </a><a href="" class="jeg_rss"><i class="fa fa-rss"></i> </a> </div> </div> </footer> <div id="statcounter"> <amp-pixel src="https://c.statcounter.com/12022999/0/02d06b5d/1/"> </amp-pixel> </div> </body> </html>