Maɓalli na waje ya buɗe ƙofar zuwa dukan duniya na bayanai
Masu zane-zane na yin amfani da makullin amfani da makullin lokacin da suke bunkasa bayanai. Daga cikin mafi mahimmancin waɗannan maɓallan shine maɓallan maɓalli da maɓallai na waje. Maballin waje na asusun waje shi ne filin a cikin teburin dangantaka wanda ya dace da maɓallin maɓallin farko na wani tebur. Don fahimtar yadda maɓallin keɓaɓɓen ke aiki, bari mu dubi ra'ayi game da bayanin haɗin kai.
Wasu Tushen Bayanan Bayanai
A cikin haɗin bayanan, an ajiye bayanai a cikin tebur da ke dauke da layuka da ginshiƙai, yana mai sauƙi don bincika da sarrafawa. Akwai wani matsala mai mahimmanci a bayyane game da batun dangantaka da dangantaka (algebra mai dangantaka, wanda EF
Codd a IBM a 1970), amma wannan ba shine batun wannan labarin ba.
Don dalilai masu mahimmanci (da wadanda ba mathematicians), haɗin bayanan yanar gizo na dangantaka "dangantaka" a layuka da ginshiƙai. Bugu da kari-kuma a nan ne inda yake samun sha'awa - mafi yawan bayanai sun tsara don haka bayanan da ke cikin tebur daya zasu iya isa ga bayanai a wani tebur. Wannan damar ƙirƙirar dangantaka tsakanin tebur shine ainihin ƙarfin haɗin bayanan.
Amfani da Ƙasashen waje
Yawancin launi, musamman ma wadanda ke cikin manyan bayanai, suna da maɓallai na farko. Tables waɗanda aka tsara don samun dama ga sauran Tables dole ne su sami maɓallin waje.
Don amfani da tushen yanar gizo mai suna Northwinds, a nan ne wani ɓangaren samfurin Tebur:
| ProductID | Sunan Sunan | CategoryID | YawanTaɗa | UnitPrice |
|---|---|---|---|---|
| 1 | Chai | 1 | 10 kwalaye x 20 bags | 18.00 |
| 2 | Chang | 1 | 24 - 12 tabarbalan gas | 19.00 |
| 3 | Sugar Aniseed | 2 | 12 - 550 ml kwalabe | 10.00 |
| 4 | Chef Anton na Cajun Seasoning | 2 | 48 - 6 na kwalba | 22.00 |
| 5 | Chef Anton's Gumbo Mix | 2 | 36 kwalaye | 21.35 |
| 6 | Grandma ta Boysenberry yada | 2 | 12 - 8 oz kwalba | 25.00 |
| 7 | Uncle Bob's Organic Dried Pears | 7 | 12 - 1 lb pkgs. | 30.00 |
Shafin ProductID shine maɓallin farko na teburin. Yana sanya ID na musamman zuwa kowane samfurin.
Wannan tebur yana ƙunshe da maɓallin maɓalli na waje, CategoryID . Duk samfurori a cikin samfur samfurin yana danganta zuwa shigarwa a cikin Teburin da ke da ma'anar wannan samfurin.
Ka lura da wannan fassarar daga cikin bayanai na Tables:
| CategoryID | CategoryName | Bayani |
|---|---|---|
| 1 | Abin sha | Abin sha masu shayarwa, caffees, teas, beers, da ales |
| 2 | Condiments | Abincin da yaji kuma mai ban sha'awa, relishes, shimfidawa, da kuma kayan yaji |
| 3 | Cutar | Desserts, candies, da sweetbreads |
| 5 | Dairy Products | Cheeses |
Rubutun na CategoryID shi ne maɓallin farko na wannan ginshiƙan. (Ba shi da maɓallin waje don ba shi da bukatar samun damar zuwa wani tebur.) Kowane maɓalli na waje a cikin samfurin Shirin yana dangantawa da maɓallin farko a cikin tebur. Alal misali, ana kiran Chai kyauta "Abin sha", yayin da Aniseed Syrup yana cikin ƙungiyar Condiments.
Irin wannan haɗi yana ƙirƙira hanyoyi da yawa don amfani da sake amfani da bayanai a cikin wani shafi na dangantaka.