Tus yuam sij txawv teb chaws qhib lub qhov rooj mus thoob ntiaj teb ntawm cov ntaub ntawv
Database designers ua kom dav siv cov yaum sij thaum tsim cov kev sib txuas lus databases. Ntawm qhov feem ntau ntawm cov yuam sij no yog cov xub tuav thiab cov yuam sij txawv teb chaws. Ib qho tseem ceeb ntawm cov ntaub ntawv database yog lub teb nyob rau hauv cov ntaub ntawv sib xws uas muaj qhov sib txawv ntawm cov kab ntawv tseem ceeb ntawm lwm lub rooj. Yuav kom nkag siab li cas ib qho tseem ceeb txawv teb chaws ua haujlwm, cia saib xyuas lub tswv yim ntawm cov ntaub ntawv sib paub zoo.
Qee cov Yaam Dlawb Database
Hauv cov ntaub ntawv sib piv, cov ntaub ntawv khaws cia hauv cov ntxhuav uas muaj cov kab thiab cov kab, ua kom yooj yim mus tshawb nrhiav thiab muab kho.Yog muaj qee qhov loj lej qab lub tswv yim ntawm cov ntaub ntawv keeb kwm (kev paub txog algebra, npaj los ntawm EF
Codd ntawm IBM hauv xyoo 1970), tab sis qhov no tsis yog lub ntsiab lus ntawm tsab xov xwm no.
Rau cov tswv yim ua lag luam (thiab cov neeg tsis paub qab hau), cov ntaub ntawv keeb kwm kev lag luam khaws ntaub ntawv "txheeb" cov ntaub ntawv ntawm cov kab thiab cov kab. Ntxiv - thiab ntawm no yog qhov twg nws tau txais kev nthuav-feem ntau databases yog tsim kom cov ntaub ntawv nyob rau hauv ib lub rooj nkag tau cov ntaub ntawv hauv lwm lub rooj. Qhov kev muaj peev xwm los tsim kev sib raug zoo ntawm cov ntxhuav yog lub zog ntawm cov ntaub ntawv sib paub zoo.
Siv Yuam Txawv Tebchaws
Feem ntau cov ntxhuav, tshwj xeeb tshaj yog cov nyob hauv loj, txoj hauv kev databases, muaj thawj cov yawm sij. Cov duab uas tsim los nkag rau lwm cov ntxhuav yuav tsum muaj qhov tseem ceeb txawv teb chaws.
Yuav siv cov ntaub ntawv feem ntau ntawm Northwinds, ntawm no yog ib qho excerpt los ntawm cov khoom rooj:
| ProductID | ProductName | Qeb | QuantityPerU | UnitPrice |
|---|---|---|---|---|
| 1 | Chai | 1 | 10 lub thawv x 20 hnab | 18.00 |
| 2 | Tseeb | 1 | 24 - 12 oz fwj | 19.00 |
| 3 | Aniseed Syrup | 2 | 12 - 550 ml hwj | 10.00 |
| 4 | Tus kws kho mob Anton tus Cajun Seasoning | 2 | 48 - 6 oz txhiab | 22.00 |
| 5 | Tus kws lij choj Anton lub Gumbo Mix | 2 | 36 lub thawv | 21.35 |
| 6 | Pog yawg Grand Boysenberry kis mus | 2 | 12 - 8 txhiab txhiab | 25.00 |
| 7 | Txiv ntxawm Bob lub Organic qhuav Pears | 7 | 12 - 1 lb pkgs. | 30.00 |
Tshooj ProductID yog cov lus saum no tus thawj qhov tseem ceeb. Nws muab tus ID cim rau txhua qhov khoom.
Cov lus no kuj muaj cov kab ntawv tseem ceeb txawv teb chaws, CategoryID . Txhua cov khoom nyob rau hauv cov khoom rooj txuas mus rau kev nkag teb chaws nyob rau hauv Pawg pawg uas txhais tias qhov khoom pawg.
Nco ntsoov no excerpt los ntawm cov database lub Rooj pawg:
| Qeb | CategoryName | Kev piav qhia |
|---|---|---|
| 1 | Haus dej haus | Haus dej qab zib, cawv, teas, beers, thiab ales |
| 2 | Txuj lom | Cov kua nplaum thiab cov khoom noj qab zib, tshuav, sib kis, thiab caij nyoog |
| 3 | Cov tshuaj tiv thaiv | Khoom qab zib, candies, thiab sweetbreads |
| 5 | Khoom noj khoom haus | Cheese |
Kem CategoryID yog kem no tus thawj qhov tseem ceeb. (Nws tsis muaj qhov tseem ceeb txawv teb chaws vim hais tias nws tsis tas siv lwm lub rooj.) Txhua txhua qhov tseem ceeb hauv cov khoom seem txuas mus rau thawj qhov tseem ceeb hauv Pawg Pawg. Piv txwv li, cov khoom Chai tau muab tso rau hauv qeb "Haus dej", thaum Aniseed Syrup yog nyob rau hauv qeb Chwv.
Qhov sib txuas ntawm no ua ib qho kev siv cov kev siv thiab rov qab siv cov ntaub ntawv hauv cov ntaub ntawv sib piv.