Apa Formulir Boyce-Codd Normal (BCNF)?

by Mike Chapple

BCNF minimizes redundancies lan mundhak integritas data

Tujuan Boyce-Codd Normal Form (BCNF) yaiku kanggo nambah integritas data kanthi ngorganisasi kolom lan tabel-tabel saka basis data relasional kanggo entuk normalisasi basis data. Normalisasi basis data dumadi nalika ana hubungan antar tabel lan nalika tabel diwenehi aturan kanggo nggawe basis data luwih fleksibel lan njaga data kasebut.

Tujuan saka normalisasi database yaiku kanggo ngilangi data sing ora ditemtokake lan kanggo njamin keterangan data nggawe pangertèn.

Database ditrapake nalika data sing padha ora disimpen ing luwih saka siji tabel lan nalika data sing gegandhengan mung disimpen ing tabel.

Asma Formula Boyce-Codd

Sawise seri pedoman, manawa database kasebut normal. Pedoman kasebut diarani minangka bentuk normal lan diétang saka siji nganti lima. A database hubungan dijelasake minangka normalisasi yen nemokake telung wangun kapisan: 1NF, 2NF, lan 3NF.

BCNF digawé minangka extension menyang wangun normal kaping tiga, utawa 3NF, ing taun 1974 dening Raymond Boyce lan Edgar Codd. Wong-wong padha nyambut gawe kanggo nggawe skema basis data sing minimalake redundansi karo tujuan ngurangi wektu komputasi. Wangun normal kaping telu ngilangi kolom sing ora gumantung ing tombol utami lan uga kanggo netepake pedoman ing wangun normal lan pisanan. BCNF, sing kadhangkala disebut minangka 3.5NF, meets kabeh persyaratan 3NF lan mbutuhake yen kunci calon ora duwe ketergantungan apa wae ing kawicaksanan ing meja.

Ing wektu nggawe BCNF, Boyce minangka salah sijine pangembang utama Structured English Query Language (SQL), sing ningkatake data kanthi cara nggunakake model hubungan Codd. Ing model iki, Codd ngandhakake yen kerumitan struktur data bisa dikurangi, sing tegese pitakon bisa luwih kuat lan fleksibel.

Nggunakake pemahaman database relasional, Codd didefinisikan pedoman 1NF, 2NF, lan 3NF. Dheweke melu karo Boyce kanggo netepake BCNF.

Calon Tunggal lan BCNF

Kunci calon yaiku kolom utawa kombinasi kolom ing tabel sing nggawé tombol unik ing basis data. Kombinasi atribut bisa digunakake kanggo ngenali rekaman database tanpa ngrujuk marang data liyane. Saben meja bisa ngemot tombol kapindho, salah siji sing bisa nduweni kunci utama. Tabel ngandhut mung siji tombol utama.

Tombol calon kudu unik.

A hubungan ing BCNF yen saben determinan minangka kunci calon. Coba tabel basis data sing nyimpen informasi pegawe lan nduweni atribut , , , lan . </p> <p> Ing tabel iki, kolom <Employee_Id> nemtokake first_name lan last_name. Kajaba iku, tuple (<First_name>, <Last_name>) nemtokake <Employee_id>. </p> <table><tbody><tr><td> <strong>Employee Id</strong> </td><td> <strong>Jeneng pisanan</strong> </td><td> <strong>Jeneng pungkasan</strong> </td><td> <strong>Judhul</strong> </td></tr><tr><td> 13133 </td><td> Emily </td><td> Smith </td><td> Manager </td></tr><tr><td> 13134 </td><td> Jim </td><td> Smith </td><td> Associate </td></tr><tr><td> 13135 </td><td> Emily </td><td> Jones </td><td> Associate </td></tr></tbody></table><p><br> Kunci calon <a href="https://jw.eyewated.com/glosarium-ketentuan-database-umum/">basis data</a> iki yaiku <Employee_Id> amarga iku mung nilai sing ora bisa digunakake dening baris liyane. </p> </div> <div class="amp-related-wrapper"> <h2>Alike posts</h2> <div class="amp-related-content"> <a href="https://jw.eyewated.com/hubungan-siji-kanggo-akeh-ing-database/"> <amp-img src="https://exse.eyewated.com/pict/dba31d5b52473311-120x86.jpg" width="120" height="86" layout="responsive" 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