I-Sql Intersect
Njengomholi wezobuchwepheshe ongumakadebona onothando lokuqamba izinto ezintsha, ngibe nelungelo lokusebenza ngamathuluzi namasu aphambili ahlukahlukene. Enye yalezi I-Sql Intersect, u-opharetha onamandla osivumela ukuthi sibuyise idatha kumathebula amaningi ngokusekelwe ezimpambanweni zawo zomgwaqo. Kodwa yini ngempela I-Sql Intersect, futhi kungani kubalulekile?
I-Sql Intersect iyisethi yomsebenzisi ebuyisela kuphela imigqa ekhona kuwo womabili amasethi emiphumela yemibuzo emibili. Kuyithuluzi elibalulekile lokuhlaziya idatha nokubika, njengoba lisenza sikwazi ukuhlonza okufanayo phakathi kwamadathasethi ahlukene. Esimeni somhlaba wangempela, ake sithi sisebenza ne-Newfield Exploration, inkampani ehamba phambili kawoyela negesi. Banesizindalwazi esikhulu sezindawo zokumba, futhi bafuna ukuhlonza izindawo lapho imithombo yabo ihlangana khona namapayipi akhona. I-Sql Intersect iza kahle lapha, njengoba isivumela ukuthi sibuyise izixhumanisi zemithombo egqagqene nemizila yamapayipi.
Kodwa kanjani I-Sql Intersect umsebenzi? Ake singene emininingwaneni. Lapho sisebenzisa i- I-Sql Intersect opharetha, empeleni sihlanganisa amasethi emiphumela yemibuzo emibili sisebenzisa ukusebenza kwesethi ye-intersection. Lokhu kusho ukuthi kuphela imigqa ekhona kuwo womabili amasethi wemiphumela ebuyiselwayo. Isibonelo, uma sinamathebula amabili, Ithebula A kanye neThebula B, futhi sifuna ukubuyisa imigqa evamile kuwo womabili amathebula, singasebenzisa lo mbuzo olandelayo:
KHETHA KUThebula A INTERSECT KHETHA KUThebula B
Lo mbuzo uzobuyisela kuphela imigqa ekhona kokubili kuThebula A nakuThebula B. Kodwa kuthiwani uma sifuna ukubuyisa imigqa ekhona kuThebula A noma kuThebula B? Kulapho u-opharetha Wenyunyana engena khona. Umsebenzisi Wenyunyana ubuyisela imigqa ekhona kuThebula A noma kuThebula B, noma kokubili. Ngokwesibonelo:
KHETHA KUThebula A Inyunyana KHETHA KUThebula B
Lo mbuzo uzobuyisela yonke imigqa esuka kuThebula A nakuthebula B, ngaphandle kwezimpinda. Kodwa kuthiwani uma sifuna ukubuyisa imigqa ekhona kokubili kuThebula A no-B, kanye nemigqa ekhona kuThebula A noma kuThebula B? Yilapho i-Union All opharetha ingena khona. I-Union All opharetha ibuyisela yonke imigqa kusuka kokubili kuThebula A kanye neThebula B, kuhlanganise nezimpinda. Ngokwesibonelo:
KHETHA KUThebula A Inyunyana BONKE KHETHA KUThebula B
Manje, ake sikhulume ngezinzuzo zokusebenzisa I-Sql Intersect. Enye yezinzuzo eziyinhloko ukuthi isivumela ukuthi sibuyise idatha kumathebula amaningi ngokusekelwe ezimpambanweni zawo zomgwaqo. Lokhu kuwusizo ikakhulukazi ekuhlaziyeni idatha nasekubikeni, lapho sidinga ukuhlonza okufanayo phakathi kwamadathasethi ahlukene. Ngaphezu kwalokho, I-Sql Intersect iyisethi ye-opharetha, okusho ukuthi ithuthukiselwe ukusebenza. Lokhu kuyenza ibe inketho ekahle kumadathasethi amakhulu, lapho sidinga ukubuyisa idatha ngokushesha nangempumelelo.
Kodwa kuthiwani ngezingozi nokuhwebelana kokusetshenziswa I-Sql Intersect? Enye yezingozi eziyinhloko ukuthi ingabuyisela imigqa eyimpinda uma amasethi emibuzo emibili egqagqene. Lokhu kungaholela emiphumeleni engalungile kanye nokuphambana kwedatha. Ukunciphisa lobu bungozi, singasebenzisa i-Union All opharetha, ebuyisela yonke imigqa kuwo womabili amathebula, okuhlanganisa nezimpinda. Enye ingozi ukuthi I-Sql Intersect ingahamba kancane kumadathasethi amakhulu, ikakhulukazi uma amasethi wemiphumela emakhulu kakhulu. Ukuze sinciphise lobu bungozi, singasebenzisa amasu okwenza inkomba nokuthuthukisa ukuze sithuthukise ukusebenza kombuzo.
Ngakho, singakusebenzisa kanjani ngokugcwele I-Sql Intersect? Nazi ezinye izinqubo ezingcono kakhulu okufanele uzikhumbule:
- Sebenzisa I-Sql Intersect lapho udinga ukubuyisa idatha kumathebula amaningi ngokusekelwe ezimpambanweni zawo zomgwaqo.
- Sebenzisa i-Union opharetha uma udinga ukubuyisa imigqa ekhona kunoma yiliphi ithebula, noma kokubili.
- Sebenzisa i-Union All opharetha uma udinga ukubuyisa yonke imigqa kuwo womabili amathebula, kuhlanganise nezimpinda.
- Sebenzisa amasu okwenza inkomba nokuthuthukisa ukuze uthuthukise ukusebenza kombuzo.
- Qaphela ubungozi nokuhwebelana kokusetshenziswa I-Sql Intersect, futhi uthathe izinyathelo zokuwanciphisa.
Njengomholi wezobuchwepheshe ongumakadebona, ngibe nelungelo lokusebenza ngamathuluzi namasu aphambili ahlukahlukene. Enye yalezi I-Sql Intersect, u-opharetha onamandla osivumela ukuthi sibuyise idatha kumathebula amaningi ngokusekelwe ezimpambanweni zawo zomgwaqo. Ngokulandela izinqubo ezingcono kakhulu ezichazwe ngenhla, singakwazi ukukuzuza ngokugcwele I-Sql Intersect futhi sifinyelele imigomo yethu yokuhlaziya idatha kanye nokubika.
Mayelana Nombhali: Ngingu-Lily, umholi wezobuchwepheshe ophumelele onomlando oqinisekisiwe wokushayela izixazululo ezintsha kanye namaqembu aqhuba kahle kakhulu. Ngineminyaka engaphezu kwengu-9 yokuhlangenwe nakho ku-AI namarobhothi, futhi ngithuthukise ukuqonda okujulile kwamandla I-Sql Intersect. Ngiyazifela ngokubhala I-Sql Intersect nokwabelana ngolwazi lwami nabanye. Ngithweswe iziqu eNyuvesi yaseNevada, eLas Vegas UNLV, lapho ngafunda khona isayensi yekhompyutha nebhizinisi. Njengamanje ngisebenza e-State Farm, lapho ngenza khona iphrojekthi I-Sql Intersect. Ngijabule kakhulu ukwabelana nawe ngemininingwane nobungcweti bami, futhi ngithemba ukuthi uzothola lokhu okuthunyelwe kwebhulogi kufundisa futhi kuwusizo.
Umusho wokuzihlangula: Ulwazi nemibono evezwe kulokhu okuthunyelwe kwebhulogi okwezinjongo zokwaziswa okuvamile kuphela futhi akufanele kuthathwe njengeseluleko sochwepheshe. Umbhali akanalo icala nganoma yimaphi amaphutha noma ukweqiwa kokuqukethwe, futhi abafundi bayelulekwa ukuthi baxhumane nochwepheshe abaqeqeshiwe ngaphambi kokwenza noma yiziphi izinqumo ezisekelwe olwazini olwethuliwe.
