Kumanzere agwirizane (SQL) - mwachitsanzo, nkhani, kugwiritsa ntchito cholakwacho

Mu zenizeni ubale Nawonso achichepere aliyense, mfundo zonse ndi anagawira pa tebulo osiyana. Ambiri a magome iikidwa mu chiwembu kulankhulana wina ndi mzake. Komabe, mothandizidwa ndi SQL mafunso zikuoneka kuika kugwirizana pakati deta, osati anapatsa dera la. Izi zachitika ndi kugwira agwirizane kugwirizana, zomwe zimathandiza inu kumanga ubale pakati pa chiwerengero cha matebulo, ndipo ngakhale kulumikiza mfundo mwakuwoneka anthuwo.

Nkhaniyi itithandiza kulankhula makamaka za akunja kumanzere agwirizane. Akuyendera kuti malongosoledwe a mtundu umenewu mogwirizana, kuwonjezera pa matebulo ena Nawonso achichepere.

Kukonzekera magome kofunika

Mwachitsanzo, mu Nawonso achichepere wathu, pali zambiri za anthu ndi chikhalidwe chawo chenicheni. Chidule zochokera matebulo atatu: Peoples (anthu), Realty (malo), Realty_peoples (maubwenzi tebulo, anthu amene zimene katundu limabweretsa). Kuganiza deta zotsatirazi kusungidwa mu magome a anthu;

Malo:

Relations anthu - katundu:

Kumanzere agwirizane (SQL) - Kufotokozera

Kumanzere pawiri ali ndi malembedwe zotsatirazi:

Ndipo schematically motere:

Ndipo mawu amenewa likumasuliridwa kuti "Sankhani zonse, popanda yekha, mzere wa Table A ndi Table B kusonyeza okha ofananira mizere ya mkhalidwe wa. Ngati tebulo inapezeka tebulo chingwe cha awiriawiri A, ndiye mudzaze mizati chifukwa Null - makhalidwe ".

Nthawi zambiri, pamene kugwirizana kumanzere imaonekera, pogwiritsa ntchito kokha pamene maina ndime, amene ankafuna kuti kugwirizana ndi chimodzimodzi.

Kumanzere agwirizane - zitsanzo za ntchito

Ndi kugwirizana kumanzere ife tikhoza kuwona, anthu onse pa mndandanda pakakhala Peoples katundu. Kuti muchite izi kumanzere agwirizane SQL kafufuzidwe Mwachitsanzo:

Ndi zotsatira izi:

Pamene ife tikuwona, Ivanova Darya Pugin Vladislav ndi Anninoy Lyubovi No mayina ufulu malo.

Ndipo kodi ife talandira, ntchito mkati agwirizane Mumtima agwirizane? Monga inu mukudziwa, kupatulako mizere sanali ofananira, kotero atatu mwa chitsanzo wathu womaliza chabe kuti waponya:

Zingatanthauze kuti Baibulo wachiwiri akukumana zikhalidwe za vuto lathu. Komabe, tikayamba angagwirizanitse mzake, ndi gome, anthu atatu chifukwa kale irretrievably wapita. Choncho, wochita, pamene kaphatikizidwe matebulo angapo kwambiri zambiri ntchito lamanzere ndi lamanja kugwirizana kuposa Mumtima agwirizane.

Adzapitiriza kuyang'ana lamanzere agwirizane zitsanzo SQL. Angagwirizanitse tebulo ndi keyala ya nyumba zathu:

Tsopano ife tikufika osati mtundu wa chilamulo, komanso adiresi ya malo:

Kumanzere agwirizane - kugwiritsa ntchito ankaikira zolakwa: Ndondomeko yosagwira tebulo

zolakwa Basic pa akunja kumanzere agwirizane matebulo awiri:

1. Molondola anasankha dongosolo la matebulo omwe deta anatayika.
2. Kodi zolakwa pamene ntchito kafufuzidwe ndi agwirizane podyerapo.

Taganizirani kulakwitsa koyamba. Isanafike chigamulo cha vuto lililonse ayenera anamvetsetsa zimene ife tikufuna kuti mapeto. Mu chitsanzo ichi pamwamba, tinatenga iliyonse mmodzi wa anthu, koma linasiiratu zokhudza chinthu pansi nambala 2, amene mwini sanapezeke.

Ngati tinasamukira magome mu kafufuzidwe mu malo ena, ndipo akanayamba ndi «... Kuyambira Realty kumanzere agwirizane Peoples ...» aliyense chuma, sitikadakhala anataya, simudzaopa za anthu.

Koma musakhale mantha kugwirizana kumanzere, kusinthana kwa zonse kunja, zomwe zili m'gulu la zotsatira ndi ofananira, osati mizere ofananira.

Ndipotu, voliyumu ya nyemba zambiri zazikulu kwambiri, ndipo deta owonjezera kwenikweni achabechabe. Chinthu chachikulu - kulingalira zimene mukufuna kupeza chifukwa: a anthu onse ndi mndandanda wa katundu wawo alipo kapena lonse mndandanda wa katundu ndi eni (ngati).

Kumanzere agwirizane - kugwiritsa ntchito ankaikira zolakwa: Funsani cholondola pamene wakhala mikhalidwe Kodi

Zolakwa chachiwiri unakambidwanso mogwirizana ndi imfa deta, ndiponso si nthawi zonse litakhala.

Tiyeni tibwerere ku funso pamene tinachoka kudzera kugwirizana analandira deta kwa anthu onse ndi chuma chawo alipo. Kumbukirani izi ndi kumanzere agwirizane Mwachitsanzo SQL:

Tiyerekeze tikufuna kulongosolerana pempho ndipo sanena linanena bungwe deta, komwe mtundu wa chilamulo - "Katundu". Ngati ife chabe append, ntchito kumanzere agwirizane SQL, chitsanzo cha chikhalidwe zotsatirazi:

...

tidzalephera deta pa anthu amene alibe chuma, chifukwa null mtengo Null si poyerekeza motere:

Pofuna kupewa zolakwa kwa zikuchitika chifukwa ichi, ndi bwino kukhazikitsa chikhalidwe kusankha pomwepo pa intaneti. Ife akusonyeza kuti zotsatirazi ndi kumanzere agwirizane Mwachitsanzo SQL.

Ndipo zotsatira zake zidzakhala motere:

Choncho, potsatira yosavuta kumanzere agwirizane Mwachitsanzo SQL, tinalandira mndandanda wa anthu onse, kusunthira patsogolo, mmodzi wa katundu izi mu chilungamo / umwini olowa.

Pamene mapeto Ndikufuna kutsindika kamodzinso chitsanzo cha mfundo iliyonse kuchokera Nawonso achichepere ayenera kumwedwa mosamala. mokoma ambiri anatsegula patsogolo pathu ndi kumanzere agwirizane Mwachitsanzo yosavuta SQL, malongosoledwe a amene - Musanayambe kulemba ngakhale kafufuzidwe zofunika, inu ayenera kumvetsa chimene ife tikufuna kuti mapeto. Zabwino zonse!