Cabanga ngesici esinjengesici
I-database inamandla kakhulu kunepredishithi efana nayo ngoba inamandla amakhulu okusesha. Ulwazi oluhlobene nolwazi olufakiwe lwe-reference-reference etafuleni ezahlukene futhi lwenza izibalo eziyinkimbinkimbi ngemali enkulu yedatha exhunyiwe. Ulwazi luhlelwe ngendlela elawulwa kalula, ifinyelelwe, futhi ibuyekeziwe.
Iyini Isici?
I- database inezintafula. Ithebula ngalinye linamakholomu nemigqa.
Umugqa ngamunye (obizwa ngokuthi i-tuple) yisethi yedatha esebenza entweni eyodwa. Ikholomu ngayinye (imfanelo) iqukethe ukuchaza izici zemigqa. Isici segciniwe yilakho igama lamakholomu kanye nokuqukethwe kwamasimu ngaphansi kwalo etafuleni ku-database.
Uma uthengisa imikhiqizo bese uyifake etafuleni enekholomu ye-ProductName, Intengo, ne-ProductID, ngayinye yalezo zihloko iyimfanelo. Ensimini ngayinye ngaphansi kwalezi zihloko, ufaka amagama womkhiqizo, amanani, kanye nama-ID womkhiqizo, ngokulandelana. Ngenye yezingeniso zensimu nakho kuyimfanelo.
Lokhu kunengqondo uma ucabanga ngakho, kunikezwe ukuthi incazelo engezona engokwemvelo yenkomba yukuthi ichaza isici noma ikhwalithi ethile.
Izimpawu Chaza Izinhlangano
Ake sicabangele i-database eyakhiwe ibhizinisi. Kungenzeka ukuthi kufaka amathebula-futhi abizwa ngokuthi yizinkampani zabakhi bezinhlelo ze-database-Amakhasimende, Abasebenzi, nemikhiqizo, phakathi kwabanye. Ithebula lemikhiqizo lichaza izici zomkhiqizo ngamunye.
Lokhu kungafaka i-ID yomkhiqizo, igama lomkhiqizo, i-ID yomphakeli (esetshenziselwa ukhiye wangaphandle ), ubungakanani, kanye nentengo. Ngayinye yalezi zici iyimfanelo yetafula (noma inhlangano) okuthiwa Imikhiqizo.
Cabanga ngalesi snippet kusuka database ekhonjwe ngokuvamile Northwinds:
| ProductID | ProductName | I-SupplierID | IsigabaID | IsibaloPerU | Intengo yokukodwa |
|---|---|---|---|---|---|
| 1 | Chai | 1 | 1 | Amabhokisi 10 x izikhwama ezingu-20 | 18.00 |
| 2 | Chang | 1 | 1 | Amabhodlela angu-24 - 12 oz | 19.00 |
| 3 | Isiraphu esisaziwayo | 1 | 2 | Amabhodlela ama-12 - 550 ml | 10.00 |
| 4 | I-Chef Anton's Cajun Seasoning | 2 | 2 | 48 - 6 oz izimbiza | 22.00 |
| 5 | I-Gumbo Mix Mix ye-Chef Anton | 2 | 2 | 36 amabhokisi | 21.35 |
| 6 | Ugogo we-Boysenberry Spread | 3 | 2 | 12 - 8 oz izimbiza | 25.00 |
| 7 | Amapheya omile omalume ka-Uncle Bob's | 3 | 7 | 12 - 1 lb ama-pkgs. | 30.00 |
Amagama ekholomu yizimfanelo zomkhiqizo. Okufakiwe emkhakheni wekholomu nakho kuyimfanelo yomkhiqizo.
Ingabe Isici Sensimu?
Ngezinye izikhathi, insimu yegama kanye nemikhiqizo isetshenziswe ngokungafani, futhi ngezinhloso eziningi, yinto efanayo. Noma kunjalo, insimu ivame ukusetshenziselwa ukuchaza iseli elithile etafuleni elitholakala kunoma yiliphi umugqa, ngenkathi isichazamazwi ngokuvamile sisetshenziselwa ukuchaza isici senkampani ngomqondo wokuklama.
Isibonelo, etafuleni elingenhla, i-ProductName emgqeni wesibili ngu- Chang . Lena yinsimu . Uma uxoxa ngemikhiqizo ngokujwayelekile, i- ProductName ikholomu yomkhiqizo. Lona umphumela.
Ungasindiswa ngalokhu. Ngokuvamile, la magama amabili asetshenziswa ngokungafani.
Ukuchaza izimfanelo
Izimfanelo zichazwe ngokwemigomo yesizinda sabo. Isizinda sichaza amanani avumelekile ukuthi lesi sici singaqukatha. Lokhu kungafaka uhlobo lwedatha, ubude, amanani, neminye imininingwane.
Isibonelo, isizinda somkhiqizo we-ProductID singacacisa uhlobo lwedatha yedatha. Imfanelo ingachazwa kabanzi ukuze idinga ubude obucacile noma icacise ukuthi ngabe inani elingenalutho noma elingaziwa livumelekile.