Iqhosha langaphandle livula umnyango kwilizwe lonke leenkcukacha
Abaqulunqi beDatabase basebenzise ngokubanzi izitshixo xa bephuhlisa iinkcukacha zolwazi. Phakathi kwezona ziqhosha eziqhelekileyo zezi zitshixo eziphambili kunye nezitshixo zangaphandle. Isiseko esingundoqo semeko yenkcubeko yangaphandle yintsimi etafileni esondeleyo efana nomqolo ophambili wecala elinye ietafile. Ukuze siqonde indlela ikrele langaphandle elisebenza ngayo, makhe sijonge ngokubhekiselele kwingcamango yolwazi olusondeleyo.
Ezinye izinto eziSeko zoLwazi lweNxulumano
Kwiziko leenkcukacha zolwazi, idatha igcinwa kwiibhile eziqulethe imigqa kunye neikholomu, okwenza kube lula ukukhangela nokusebenzisa. Kukho izibalo ezinzulu emva kwengcamango yolwazi olunxulumeneyo (i-algebra yobudlelwane, ecetywayo yi-EF
I-Codd kwi-IBM ngo-1970), kodwa asiyiyo isihloko sale nqaku.
Ngeenjongo ezifanelekileyo (kunye nabangewona imathematika), i-database yolondolozo "idibene" idatha kwimigca kunye neentsika. Ukuqhubela phambili-kwaye nantsi apho ithola umdla-ininzi yolwazi yenzelwe ukuba idatha kwitafile enye ikwazi ukufikelela kwedatha kwelinye itafile. Oku kukwazi ukudala ubudlelwane phakathi kweetable kuwona mandla okwenene yedatha yolwazi.
Ukusebenzisa iiKhenketho zangaphandle
Uninzi lwetafile, ngokukodwa ezo zinto zininzi, zineenkcukacha eziphambili. Iifayile ezenzelwe ukufikelela kwezinye iitheyibhile kufuneka zibe nekona yangaphandle.
Ukusebenzisa isiseko seenkcukacha seNorthwinds esichazwe ngokuqhelekileyo, nantsi inkcazo evela kwiThebula lomkhiqizo:
| ProductID | Igama lemveliso | CategoryID | UbungakananiPerU | Ixabiso lento |
|---|---|---|---|---|
| 1 | Chai | 1 | Iibhokisi ezili-10 x 20 iibhegi | 18.00 |
| 2 | Tshintsha | 1 | Iibhola ze-oz 24-12 | 19.00 |
| 3 | Isiraphu esisikiweyo | 2 | 12 - 550 iibhotile | 10.00 |
| 4 | I-Chef Anton's Cajun Seasoning | 2 | 48 - 6 izitya ze-oz | 22.00 |
| 5 | I-Chef Anton's Gumbo Mix | 2 | 36 iibhokisi | 21.35 |
| 6 | U-Grandm's Boysenberry Usasazeka | 2 | 12 - 8 izitya | 25.00 |
| 7 | Amalume aseMal Bob's Organic Omebileyo | 7 | 12 - 1 lb pkgs. | 30.00 |
Ikholomu ye- ProductID yiyona nto iphambili yetafile. Ikwazisa i-ID ekhethekileyo kwimveliso nganye.
Le tafile iqulethe ikholomu yangaphandle yekhowudi, i- CategoryID . Yonke imveliso kwitheyibhile yomveliso idibanisa nokungena kwiibhola zetekisi ezichaza uluhlu lwemveliso.
Qaphela le nkcazo kwi-table Categories yamagama:
| CategoryID | INameName | Inkcazo |
|---|---|---|
| 1 | Utywala | Iziphuzo ezinxilisayo, ii-coffees, iifayi, iibhiya kunye ne-ales |
| 2 | ICondiments | Iisusi ezinomsoco ezinomsoco, ukuhlaziya, ukusabalalisa, kunye neenkqubela |
| 3 | Ukudibanisa | Iidayisi, ii-candies, kunye namaqabunga |
| 5 | Iimveliso zederi | Ieshizi |
I-ID yekholomu yekhowudi yile nkcazo ephambili yikholamu. (Ayinanto yokwamanye amazwe ngenxa yokuba ayinaso isidingo sokufikelela kwelinye itafile.) Zonke iikhiye zangaphandle kwiTheyibhile yomkhiqizo zidibanisa ukhiye ophambili kwimigangatho yeetafile. Ngokomzekelo, umkhiqizo we-Chai unikezwa udidi lwe "Iingxowa", ngoxa i-Aniseed Siraphu iluhlu lweCodediments.
Olu hlobo lokudibanisa ludala iindlela ezininzi zokusebenzisa nokuphinda usetyenzise idatha kwiziko lolwazi.