Cinga ngombono njengempawu
I-database isamandla kunokuba ispredishithi ifana nayo kuba inamandla amakhulu okukhangela. Iinkcukacha zobudlelwane ezinxulumene nomgca weefayile ezihlukeneyo kwaye zenze izibalo ezinzima kwixabiso elikhulu leenkcukacha ezidibeneyo. Ulwazi luququzelelwe ngendlela elawulwa lula, ifumaneka kwaye ihlaziywe.
Yiyiphi impawu?
Isiseko sedatha sinamatafula. Itafile nganye inemihlathi kunye nemigqa.
Umqolo ngamnye (obizwa ngokuba yi-tuple) yiseti yedatha esebenza kwinto enye. Ikholam nganye (umxholo) iqulethe ukuchaza iimpawu zemiqolo. Isalathisi sesiseko sedata ligama lekholomu kunye nomxholo weenkalo phantsi kwayo kwitheyibhile kwisiseko sedatha.
Ukuba uthengisa iimveliso uze uzifake kwitafile kunye neikholomu ze-ProductName, Intengo, kunye ne-ProductID, nganye yezo zihloko ziyimpawu. Kwintsimi nganye phantsi kwezo zihloko, ufaka amagama emveliso, amaxabiso, kunye nee-ID zeemveliso, ngokulandelanayo. Ngamanye amabango angenayo yinkalo.
Oku kunengqiqo xa ucinga ngako, unikwe ukuba inkcazo engeyiyo yonkqenkqiso yembonakalo kukuba ichaza uphawu okanye umgangatho othile.
Iimpawu Zichaza Amacandelo
Makhe sicinge ngedatha ephuhliswe ishishini. Kusenokwenzeka ukuba kubandakanya iitafile-ezibizwa ngokuba ngamacandelo abaqulunqa i-database-kubaThengi, Abasebenzi kunye neMveliso, phakathi kwabanye. Itheyibhile yeeMveliso ichaza iimpawu zemveliso nganye.
Ezi zingabandakanya i-ID yomkhiqizo, igama lomkhiqizo, i-ID yomthengisi (isetyenzisiweyo njengokhiye wangaphandle ), ubuninzi, kunye nexabiso. Ngayinye yale mpawu yinkalo yetafile (okanye iqumrhu) elibizwa ngokuba yiMveliso.
Cinga ngolu hlobo lweenkcukacha kwi-database ye-Northwinds ekhankanywe ngokuqhelekileyo:
| ProductID | Igama lemveliso | UmthengisiID | CategoryID | UbungakananiPerU | Ixabiso lento |
|---|---|---|---|---|---|
| 1 | Chai | 1 | 1 | Iibhokisi ezili-10 x 20 iibhegi | 18.00 |
| 2 | Tshintsha | 1 | 1 | Iibhola ze-oz 24-12 | 19.00 |
| 3 | Isiraphu esisikiweyo | 1 | 2 | 12 - 550 iibhotile | 10.00 |
| 4 | I-Chef Anton's Cajun Seasoning | 2 | 2 | 48 - 6 izitya ze-oz | 22.00 |
| 5 | I-Chef Anton's Gumbo Mix | 2 | 2 | 36 iibhokisi | 21.35 |
| 6 | U-Grandm's Boysenberry Usasazeka | 3 | 2 | 12 - 8 izitya | 25.00 |
| 7 | Amalume aseMal Bob's Organic Omebileyo | 3 | 7 | 12 - 1 lb pkgs. | 30.00 |
Amagama ekholomu ziimpawu zeemveliso. Okufakwe kwiinkalo zamakholomu nazo ziyimpawu zemveliso.
Ingummiselo wendawo?
Ngamanye amaxesha, intsimi yexesha kunye nesibonakaliso zisetyenziswa ngokungafaniyo, kwaye ngeenjongo ezininzi, zifana noko. Nangona kunjalo, inkundla isetyenziselwa ukuchaza iseli ethile etafileni efunyenwe kuyo nayiphi na umqolo, ngelixa i- attribute isetyenziswa ngokubanzi ukuchaza uphawu lwesigqeba kwindlela yokuyila.
Umzekelo, kwitheyibhile elingentla, uMkhiqizoName kumqolo wesibini nguTshintsho . Le yintsimi . Ukuba uxoxa ngeemveliso ngokubanzi, ProductName ikholomu yomkhiqizo. Oku kuyimpawu .
Musa ukuxhoma kule nto. Ngokuqhelekileyo, le mibini mibini isetyenziswe ngokungafaniyo.
Ukuchaza iiMpawu
Iimpawu zichazwe ngokwemiqathango yazo. Idibansi ichaza ixabiso elivunyelwe ukuba le nxalenye ingaba nayo. Oku kungabandakanya uhlobo lwedatha, ubude, ixabiso kunye nezinye iinkcukacha.
Ngokomzekelo, i- domain ye- ProductID yomxholo ingacacisa uhlobo lolwazi lwenombolo. Isalathiso sinokuchazwa ngakumbi ukuba sidinga ubude obuthile okanye icacise ukuba ixabiso elingenanto okanye elingaziwa livumelekile.