Mune zvishoma zvisingabatsiri kushandiswa pane chimwe chinhu chidimbu cheumwe
Munyika yenhau dzezvekodzero dzekodzero, kushandiswa kwebasa kunowanikwa apo chimwe chirevo chinogadzira chimwe chimiro chinonyanya mu database. Chinhu chiduku chinoshandiswa pakuzvidzivirira ndezvekuchengetedzwa kwebhuku rinowanikwa apo rinotsanangura kushanda kwekushanda kwechiratidzo kana chekuunganidza kwezvimiti zvinosanganisira chimiro chepakutanga.
Mienzaniso yekusakosha kunoshanda
Rudzi urwu rwekutendwa runonzi ruduku nokuti runogona kubva pane unyanzvi. Kana imwe "rutivi" ichinyorwa cheimwe, inonzi yakashata. Rutivi rworuboshwe runofungidzirwa kuti ndiro rakagadzirisa uye rakarurama rinotarisirwa .
- [A, B} -> B isingabatsiri kuita basa nokuti B ichinyorwa cheA, B. Kubva { A, B} -> B inosanganisira B , kukosha kweB kunogona kugadziriswa. Icho chinhu chiduku chekuita basa nokuti kutarisa B kunogutsikana nehukama hwayo neA, B. Sezvo hutsika dzeB dzakagadzirirwa nehutsika hweA , humwe humwe hutano hunogovera hutsika hweA huchava nemafungiro akafanana seB . Imwe nzira yekuisa nayo ndeyokuti yose yeB inowanikwa muA , ndicho chikonzero icho chiri s subset.
- {Employee_ID, Employee_Name} -> Employee_ID inoshandawo zvishoma kudarika sezvo Employee_ID iri chikamu che {Employee_ID, Employee_Name} .
- Izvozvowo ndezveA -> A kana Employee_ID -> Employee_ID, uye Employee_Name-> Employee_Name . Izvi zvose zvisingabatsiri zvinoshanda.
- Kana kushandiswa kwebasa X-> Y, uye Y i-subset ye X, ichi chinhu chisina basa chekuchengetedza. Kana Y isisi yechinyorwa che X, izvi hazvisi zvishoma zvisingabatsiri.