Zer da Boyce-Codd Normal Forma (BCNF)?

BCNFek gutxieneko erredundantzia eta datu osotasuna handitzen du

Boyce-Codd Normal Formaren (BCNF) helburua datuen osotasuna areagotzea da datu baseen datu baseak zutabeak eta taulak antolatzea datu baseen normalizazioa lortzeko. Datu-basearen normalizazioa mahaien artean ezarrita dagoenean gertatzen da eta taulak definitutako arauek datu-basea malgutasun handiagoa izan dezaten eta datuak gordetzeko.

Datu-basearen normalizazioaren helburuak datu erredundanteak ezabatzea eta datuen mendekotasunak zentzua izatea da.

Datu-basea normalizatu egiten da datu berberak taula bat baino gehiago gordetzen ez badira eta mahai batean gordetako datuak bakarrik gordetzen direnean.

Boyce-Codd jatorria Formulario arrunta

Jarraibide batzuk jarraituz, datu-baseak normalizatu egiten direla bermatzen da. Jarraibide hauek forma arrunt gisa aipatzen dira eta bostetik bederatzietatik zenbatzen dira. Datu-base erlazional bat normalizatzen da lehen hiru formak betetzen baditu: 1NF, 2NF eta 3NF.

BCNF hirugarren formatu normalera edo 3NFraino luzatu zen, 1974an Raymond Boyce eta Edgar Codd-ekin. Gizonak datu-baseko eskemak sortzeko lanean ari ziren, konputazio-denbora murrizteko helburua murrizteko helburuarekin. Hirugarren formatu arruntek lehen mailako gakoaren menpekoak ez diren zutabeak ezabatzen dituzte lehen eta bigarreneko formen jarraibideak betetzeko. BCNF, 3.5NF gisa aipatzen dena, 3NFren eskakizun guztiak betetzen ditu eta hautagai gakoak ez ditu mahai batean beste atributuren menpekorik.

BCNF-ren sorkuntzaren garaian, Boyce English Query Language Structured Structured (SQL) garapen gakoetako bat izan zen, Codd-en erlazio eredua erabiliz datuen berreskurapena hobetuz. Eredu horretan, Codd-ek datu-baseen konplexutasun estrukturala murriztu egin zezakeen, horrek esan nahi du kontsultak ahaltsuagoak eta malguak izan zitezkeela.

Bere datu-baseen datu base erlazionalak erabiliz, Coddek 1NF, 2NF eta 3NF jarraibideak definitu zituen. Boyce-rekin bat egin zuen BCNF definitzeko.

Candidate Keys eta BCNF

Hautagaiaren gako bat zutabe edo konbinazio bat da datu-basean gako bakarra osatzen duen taulan. Atributuen konbinazioa datu-basearen erregistroa identifikatzeko erabil daiteke datuen arabera. Mahai bakoitzak hautagai hautazko teklak izan ditzake, eta horietako batek lehen mailako gakoak izan ditzake. Taula batek lehen mailako tekla bakarra dauka.

Hautagaien gakoak bakarra izan behar du.

Erlazio bat da BCNFen determinatzaile bakoitza hautagai gako bat bada. Ikertu langileentzako informazioa gordetzen duen datu-basearen taulan eta atributuak, , eta . </p> <p> Taula honetan, <Langilearen_Id> eremua first_name eta last_name zehazten ditu. Era berean, tupla (<First_name>, <Last_name>) zehazten du <Employee_id>. </p> <table><tbody><tr><td> <strong>Langilearen Id</strong> </td><td> <strong>Izena</strong> </td><td> <strong>Abizena</strong> </td><td> <strong>Izenburua</strong> </td></tr><tr><td> 13133 </td><td> Emily </td><td> Smith </td><td> Kudeatzailea </td></tr><tr><td> 13134 </td><td> Jim </td><td> Smith </td><td> elkartua </td></tr><tr><td> 13135 </td><td> Emily </td><td> Jones </td><td> elkartua </td></tr></tbody></table><p><br> <a href="https://eu.eyewated.com/baldintza-orokorren-datu-terminoen-glosarioa/">Datu-base</a> honen hautagaiaren gakoa <Employee_Id> da, beste errenkada bat erabili ezin duen bakarra delako. </p> </div> <div class="amp-related-wrapper"> <h2>Alike posts</h2> <div class="amp-related-content"> <a href="https://eu.eyewated.com/candidate-key-definizioa/"> <amp-img src="https://exse.eyewated.com/pict/e331fa6998313ef0-120x86.jpg" width="120" height="86" layout="responsive" 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