Ụdị ọdịdị nke atọ (3NF) bụ ụkpụrụ nchekwa data nke na-akwado nkwenye nke data site na iwukwasị na ụkpụrụ normalization nke data nyere site na Ụdị Nkịtị Mbụ (1NF) na Ụdị Iwu Abụọ (2NF).
Ụdị Nlereanya Nke Atọ
Enwere ihe abụọ dị mkpa maka nchekwa data iji bụrụ ụdị nke atọ:
- Ntọala data ga- emezurịrị nke chọrọ 1NF na 2NF .
- Ogige nchekwa data niile ga-adabere na isi ihe dị mkpa , nke pụtara na uru nke kọlụm ọ bụla nwere ike isi na isi isi.
Banyere Isi Ihe Ntubere Isi
Ka anyị nyochaa ihe anyị na-eche n'eziokwu bụ na akụkụ niile ga-adabere na isi ihe dị mkpa.
Ọ bụrụ na uru kọlụm nwere ike inweta site na isi isi na kọlụm ọzọ na tebụl, ọ na-emebi 3NF. Tụlee table nke ndị ọrụ na ogidi ndị a:
- Onye ọrụ
- Aha mbụ
- Aha ikpeazụ
Ndi aha aha na aha mbu bu nani na uru nke EmployeeID? Ọfọn, aha aha pụrụ ịdabere na FirstName? Ee e, n'ihi na ọ dịghị ihe dị n'ime aha LastName ga-atụ aro uru FirstName. Nwa mbu nwere ike igbenye n'aha aha? Ozoghi, n'ihi na otu a bu eziokwu: ihe obula aha aha nwere ike ibu, o nwegh ike inye ihe omuma dika uru FirstName. Ya mere, okpokoro a bụ ntinye 3NF.
Ma tụlee nke a Vehicules table:
- VehicleID
- Emeputa
- Nlereanya
Emeputa na Ihe Nlereanya nwere ike inweta site na VehicleID - mana Ụkpụrụ ahụ pụkwara inweta site na emeputa n'ihi na otu onye na-emepụta ihe na-emepụta ụgbọala. Nzube tebụl a abụghị nke 3NF kwadoro, ya mere, ọ nwere ike, na-akpata nchịkwa data. Dịka ọmụmaatụ, ịnwere ike imelite onye na-emeputa n'emezigharị ihe nlereanya ahụ, na-ebute na-ezighị ezi.
Iji mee ka o kwekọọ, ọ ga-adị mkpa ka ị kwaga kọlụm ọzọ na-esote na tebụl ọzọ ma kwuo ya iji isi mba ọzọ. Nke a ga - eweta tebụl abụọ:
Ugbo ala
Na tebụl n'okpuru, ModelID bụ isi mba ọzọ na tebụl Ụdị :
- VehicleID
- Emeputa
- ModelID
Ụdị Ụdị
Ụdị map ndị a na-erepụta ndị na-emepụta ihe. Ọ bụrụ na ịchọrọ imelite ozi ọ bụla ụgbọ ala kpọmkwem na ihe nlereanya, ị ga-eme ya na tebụl a, karịa na tebụl Vehicules.
- ModelID
- Emeputa
- Nlereanya
Ala ndị a chọtara na Model 3NF
Tebụl nwere ike ịnwe ala a nwetara - nke a na-atụle dabeere na ogidi ndị ọzọ na tebụl. Dịka ọmụmaatụ, tụlee tebụl a nke iwu wijetị:
- Nọmba ịtụ ahịa
- Nọmba ahịa
- Ọnụahịa otu
- Ọnụ ọgụgụ
- Ọnụ
Mkpokọta ahụ agbajiri nkwenye 3NF n'ihi na ọ nwere ike ịmalite site n'ịba ụba ọnụahịa unit site na nnukwu, kama ịdabere kpamkpam isi isi. Anyị ga-ewepu ya na tebụl iji mee ụdị nke atọ.
N'ezie, ebe ọ bụ na ọ na-enweta ya, ọ ka mma ịghara ịchekwa ya na nchekwa data ahụ ma ọlị.
Anyị nwere ike ịkọwa ya "na ada" mgbe ị na-aza ajụjụ ntanetịime. Dịka ọmụmaatụ, anyị nwere ike iji nyocha a iji weghachite nọmba ọnụọgụgụ na ụda:
CHINE OrderNumber, Nzuzo na WidgetOrdersAnyị nwere ike iji ajụjụ na-esonụ:
Hụ OrderNumber, UnitPrice * Ọnụ ọgụgụ AS Total FROM WidgetOrdersiji mezuo otu ihe ahụ ma ọ bụrụ na ị ghara imebi ụkpụrụ normalization.