Txhob Txhob Txim Rau Qhov Hloov Rau Kev Pab Txhawb Kom Txhim Kho
Kev vam meej nyob hauv qhov chaw khaws ntaub ntawv yog ib qho kev tsis sib raug ntawm qhov tseem ceeb hauv tib lub rooj uas ua rau muaj kev ua haujlwm zoo . Kom ua tau raws li tus txheej txheem ntawm Normalization Standard (3NF), koj yuav tsum tau tshem tawm cov kev hloov ntawm kev hloov.
Los ntawm cov xwm txheej, qhov kev vam meej yuav tsum muaj peb los yog ntau dua cov cwj pwm (los yog cov ntaub ntawv database) uas muaj kev tswj hwm ntawm lawv, txhais tau hais tias Kem A nyob rau hauv ib lub rooj cia siab rau kem B los ntawm ib nrab sab C.
Cia peb pom tias qhov no yuav ua haujlwm li cas.
Kev Piv Txwv Kev Hloov Siab
TSO CAI
| Author_ID | Sau | Phau ntawv | Author_Nationality |
|---|---|---|---|
| Auth_001 | Orson Scott Card | Ender's Game | Tebchaws Asmeskas |
| Auth_001 | Orson Scott Card | Ender's Game | Tebchaws Asmeskas |
| Auth_002 | Margaret Atwood | Tus Handmaid's Taleus | Canada |
Hauv PAUV TSEEJ saum toj no:
- Phau ntawv → Sau : Ntawm no, Phau Ntawv tus cwj pwm txiav txim siab Tus Neeg Tus Cwj Pwm. Yog tias koj paub lub npe ntawm phau ntawv, koj tuaj yeem kawm tus sau lub npe. Txawm li cas los xij, Tus Sau tsis txiav txim siab phau ntawv , vim tias tus sau tau ntawv sau tau ntau phau ntawv. Piv txwv li, vim peb paub tus sau lub npe Orson Scott Card, peb tseem tsis tau paub lub npe ntawm phau ntawv.
- Sau ntawv → Author_Nationality : Ib yam li, Tus Author attribute txiav txim rau Author_Nationality , tab sis tsis rau lwm txoj kev ncig; vim hais tias peb paub cov haiv neeg tsis txhais hais tias peb tuaj yeem txiav txim siab rau tus sau.
Tab sis cov lus qhia no qhia txog kev tuaj yeem hloov siab:
- Phau ntawv → Author_Nationality: Yog peb paub phau ntawv npe, peb tuaj yeem txiav txim seb lub tebchaws twg ntawm tus Sau Sau.
Kev Zam Tsis Muaj Kev Tuaj Rau Kev Hloov
Yuav kom paub tseeb Daim Ntawv Teev Tseg Peb, tshem tawm txoj kev pabcuam raws sijhawm.
Peb tuaj yeem pib los ntawm Tshooj Phau Ntawv ntawm cov lus sau Authors thiab tsim kom muaj cov phau ntawv cais:
PHAU NTAWV
| Book_ID | Phau ntawv | Author_ID |
|---|---|---|
| Phau ntawv no | Ender's Game | Auth_001 |
| Phau ntawv no | Cov me nyuam ntawm lub siab | Auth_001 |
| Book_002 | Tus Handmaid's Taleus | Auth_002 |
TSO CAI
| Author_ID | Sau | Author_Nationality |
|---|---|---|
| Auth_001 | Orson Scott Card | Tebchaws Asmeskas |
| Auth_002 | Margaret Atwood | Canada |
Puas tau kho qhov no? Cia peb kuaj xyuas peb cov kev pab cuam tam sim no:
COV NTAWV COV NTAWV :
- Book_ID → Phau ntawv: Phau ntawv nyob ntawm phau ntawv .
- Tsis muaj lwm yam kev pab cuam nyob rau hauv cov lus no, peb thiaj li yog. Nco ntsoov tias tus yuam sij txawv teb chaws Author_ID txuas mus rau hauv rooj lus no rau AUTHORS cov lus los ntawm nws tus thawj tseem ceeb Author_ID . Peb tau tsim muaj kev sib raug zoo kom tsis txhob muaj kev vam meej, qhov tseem ceeb ntawm txoj kev sib txuas lus.
COV TSWV HUV :
- Author_ID → Sau: Tus Sau yog nyob ntawm tus Author_ID .
- Sau ntawv → Author_Nationality: Lub tebchaws yuav txiav txim los ntawm tus sau.
- Author_ID → Author_Nationality: Lub tebchaws tuaj yeem txiav txim tau los ntawm Author_ID los ntawm tus sau attribute. Peb tseem muaj kev vam meej tuaj.
Peb yuav tsum ntxiv cov lus thib peb rau cov ntaub ntawv no:
LUB TEB CHAWS
| Country_ID | Lub teb chaws |
|---|---|
| Coun_001 | Tebchaws Asmeskas |
| Coun_002 | Canada |
TSO CAI
| Author_ID | Sau | Country_ID |
|---|---|---|
| Auth_001 | Orson Scott Card | Coun_001 |
| Auth_002 | Margaret Atwood | Coun_002 |
Tam sim no peb muaj peb lub rooj, uas siv cov thawv txawv teb chaws mus txuas ntawm cov ntxhuav:
- Cov BOOK rooj lus qhov tseem ceeb txawv Author_ID sib txuas rau ib phau ntawv rau tus sau hauv daim duab TSO CAI.
- TSO TSWV TSEV cov lus teb chaws txawv teb chaws Country_ID txuas mus rau ib lub teb chaws hauv lub teb chaws.
- Lub rooj teb chaws tsis muaj lub ntsiab lus txawv teb chaws vim hais tias nws tsis tas yuav txuas rau lwm lub rooj hauv qhov tsim.
Vim Li Cas Thiaj Muaj Kev Nyuaj Hloov Kho Dua Tshiab Tsim
Dab tsi yog qhov tseem ceeb ntawm kev tsis txhob muaj kev vam meej txuas mus pab txhawm rau 3NF? Cia peb xav txog peb cov lus xub thawj dua thiab pom cov teeb meem nws tsim:
TSO CAI
| Author_ID | Sau | Phau ntawv | Author_Nationality |
|---|---|---|---|
| Auth_001 | Orson Scott Card | Ender's Game | Tebchaws Asmeskas |
| Auth_001 | Orson Scott Card | Cov me nyuam ntawm lub siab | Tebchaws Asmeskas |
| Auth_002 | Margaret Atwood | Tus Handmaid's Taleus | Canada |
Hom kev tsim no tuaj yeem pab txhawb rau cov ntaub ntawv sib thooj thiab tsis haum, piv txwv:
- Yog hais tias koj deleted ob phau ntawv "Cov me nyuam ntawm lub siab" thiab "Ender's Game," koj yuav rho tawm tus sau "Orson Scott Card" thiab nws haiv neeg tag nrho ntawm cov ntaub ntawv.
- Koj tsis tuaj yeem sau tus sau dua tshiab rau qhov database tshwj tsis yog koj ntxiv ib phau ntawv; dab tsi yog tias tus sau tsis tau muaj ntawv tshaj tawm lossis koj tsis paub lub npe ntawm ib phau ntawv uas nws tau sau lawm?
- Yog tias "Orson Scott Card" hloov nws haiv neeg, koj yuav tau hloov nws cov ntaub ntawv uas nws tshwm. Muaj ntau cov ntaub ntawv nrog tus sau tib neeg tuaj yeem ua rau cov ntaub ntawv tsis muaj tseeb: ua li cas yog tias cov ntaub ntawv nkag tus neeg tsis paub nws muaj ntau yam ntaub ntawv rau nws thiab hloov cov ntaub ntawv hauv ib daim ntawv teev xwb?
- Koj tsis tuaj yeem rho tawm ib phau ntawv zoo li "The Handmaid's Tale" tsis tau hais tias tus sau tag nrho.
Cov no tsuas yog qee yam yog vim li cas kev coj ua , thiab tsis txhob muaj kev sib raug zoo, tiv thaiv cov ntaub ntawv thiab xyuas kom meej.