Iyi mitemo miviri iri nyore ichatsigira normalizing your database
Fomu Yokutanga Yakarongeka (1NF) inogadzirisa mitemo inokosha ye database yakarongeka:
- Bvisa zvinyorwa zvinyorwa kubva patafura rimwe chete.
- Gadzira mahwendefa akaparadzana eboka rega rega re data rakanamatira uye ona mutsara mumwe nomumwe nekamuri yakasiyana-siyana (inokosha yekutanga).
Ko mitemo iyi inorevei paunofunga nezvekugadzirwa kwebhuku re database? Ichokwadi chaizvo.
1. Kurega Kudzokorora
Mutemo wekutanga unotaurira kuti hatifanire kudhinda deta mukati memutsara mumwechete we tafura. Munharaunda yemagariro evanhu, pfungwa iyi inotumidzwa seatomicity ye tafura. Matafura anoteerera mutemo uyu anonzi atomic. Ngationgororei nheyo iyi nemuenzaniso wekare: tafura mukati mehutori hwehupfumi hwevanhu hunochengetedza hutano-hukuru hwehukama. Nechinangwa chemuenzaniso wedu, tichaisa mutemo webhizimisi kuti mutungamiriri wega wega angave neavo kana vamwe vanomiririra apo umwe neumwe angave ane maneja mumwe chete.
Intuitively, pakusarudza rondedzero kana pepanheti kuti uite izvi, tinogona kugadzira tafura neminda inotevera:
- Manager
- Subordinate1
- Subordinate2
- Subordinate3
- Subordinate4
Zvisinei, yeuka mutemo wekutanga wakagadzirirwa neNNF: Bvisa zvinyorwa zvinyorwa kubva patafura rimwe chete. Zvakajeka, avo vari pasi -1-Subordinate4 zvikamu zvinodzokorora. Tora kanguva ufungisise matambudziko akataurwa nemamiriro ezvinhu aya. Kana maneja ane imwe chete, iyo Subordinate2-Subordinate4 zvinyorwa zvinongorasikirwa nzvimbo yekuchengetedza (chinhu chinokosha chezvinhu zvemasitadhi). Uyezve, fungidzira nyaya iyo maneja anenge atova nevanomiririra 4 - chii chinoitika kana iye akatora kune umwe mushandi? Iyo yose tafura yakarongeka inoda kuchinjwa.
Parizvino, pfungwa yechipiri yakajeka kazhinji inowanikwa kune zvinyorwa zvepa database: Hatidi kuva nekoramende imwe uye isu tinoda kubvumira kuwanda kwemari yekuchengetedza deta. Ngatiedzei chimwe chinhu chakadai:
- Manager
- Vakuru
Uye munda wakaderera unenge uine zvinyorwa zvakawanda mumutauro "Maria, Bill, Joe."
Iri sarudzo riri pedyo, asi rinowirawo pfupi pane chiratidzo. Chikamu chemuzasi chinoramba chichinyorwa uye chisina-atomu. Chii chinoitika kana tichida kuwedzera kana kubvisa pasi? Tinofanira kuverenga uye kunyora zvose zviri mukati meetafura. Icho hachisi chinhu chikuru mumamiriro ezvinhu aya, asi zvakadini kana mumwe maneja ane vashandi zana? Uyewo, zvinosanganisira nzira yekusarudza dheta kubva kune d database mumibvunzo inotevera.
Heino tafura inogutsa murairo wekutanga weNNF:
- Manager
- Subordinate
Muchiitiko ichi, umwe neumwe pasi ane chinyorwa chimwe chete, asi vatungamiri vanogona kuva nezvinyorwa zvakawanda.
2. Ziva Chinokosha Chinokosha
Zvino, zvakadini nemitemo yechipiri: ona mutsara wega wega nehomwe yakasiyana-siyana kana seti yemakoroni ( inokosha yekutanga )? Iwe unogona kutarisa tafura iri kumusoro uye kuratidza kushandiswa kwendarama yakasimwa sechinhu chikuru. Ichokwadi, chikamu chemukati ndeye mukana wakanaka wepfungwa huru nekuda kwekuti bhizinesi redu rinotonga kuti umwe neumwe ari pasi angave nemutungamiriri mumwe chete. Zvisinei, data yatakasarudza kuchengeta tafura yedu inoita izvi zvishoma kudarika nzira yekugadzirisa. Chii chinoitika kana tikashandira mumwe mushandi anonzi Jim? Tinochengetedza sei hutano hwake-mutungamiri-pasi mumadhekisi?
Zvakanakisisa kushandisa chinyorwa chaicho chakasiyana (zvakadai seIndaneti yevashandi) sekiyi yekutanga . Tafura yedu yokupedzisira yaizoita seyiyi:
- Manager ID
- Subordinate ID
Iye zvino, tafura yedu iri mufomu yepakutanga! Kana iwe uchida kuramba uchidzidza nezvekusimudzira, verenga zvimwe zvikamu munyaya dzino dzakatevedzana: