Ukubuyisela iData kwiiTable ezininzi kunye ne-SQL yangaphakathi

Ukungena kwangaphakathi kubuyisela ulwazi oluvela kwiinkcukacha ezimbini okanye ngaphezulu

Ukujoyina kwangaphakathi zihlangene rhoqo kwiSQL. Babuyela kuphela ulwazi olukhoyo kumatafula amabini okanye ngaphezulu. Umgangatho wokujoyina unquma ukuba yeyiphi iirekhodi ezidibeneyo kunye kwaye zichazwe kwicandelo LAPHO. Ngokomzekelo, ukuba ufuna uluhlu lwamatriki / imoto esetyenziswa kuyo zombini isithuthi kunye nomqhubi kwi-dolophu efanayo, umbuzo olandelayo we SQL ufezekisa lo msebenzi:

HLOLA igama lokugqibela, igama lo kuqala, itekethi KWABASEBENZI abaqhubi, izithuthi ABAKHO abaqhubi

Nazi iziphumo:

Igama lokuqala igama
----------- ------------ ----
Baker Roland H122JM
Smythe Michael D824HA
Smythe Michael P091YF
Jacobs Abraham J291QR
Jacobs Abraham L990MT

Qaphela ukuba iziphumo zifunwa ngokuthe ngqo. Kunokwenzeka ukuhlaziya umbuzo ngokucacisa iikhrayitheriya ezongezelelweyo kwiCANDELO LOMHLABA. Cinga ukuba umbuzo oyimfuneko ufanisa abaqhubi kwizithuthi ezingagunyazisiweyo ukuqhuba (abaqhubi beloli ukuya emotweni kunye nakwezinye izinto). Unokusebenzisa umbuzo olandelayo ukulungisa le ngxaki:

HLOLA igama lokugqibela, igama, itekiti, izithuthi.klasi ukusuka kubaqhubi, izithuthi apho ABASEBENZI.Izixhobo = izithuthi.nxibelelwano kunye nabaqhubi.class = izithuthi.class

Lo mzekelo ucacisa itheyibhile yenkcazo yenkalo yeklasi kwiSIGABA sokukhetha ngoba iklasi lingenangqondo-ibonakala kuzo zombini iitheyibhile. Ikhowudi yayiza kubonisa ukuba yeyiphi ikholamu yetafile kufuneka ifakwe kwimiphumo yemibuzo. Kule meko, ayenzi umehluko, njengoko iikholomu zifana kwaye zijoyina usebenzisa i-equijoin. Nangona kunjalo, ukuba iikholomu ziqulethe iinkcukacha ezahlukeneyo, lo mahluko uza kuba lukhulu. Nazi iziphumo zalo mbuzo:

Igama lokugqibela lomnxeba
---------- ------------ ---- ------
Baker Roland H122JM Imoto
Smythe Michael D824HA Iloliwe
Jacobs Abraham J291QR Imoto

Imigca ekhoyo ehambelana noMichael Smythe emotweni kunye no-Abraham Jacobs kwiloli, izithuthi ezingagunyaziswanga ukuqhuba.

Ungaphinda usebenzise ukujoyina kwangaphakathi ukudibanisa idatha kwietrafti ezintathu okanye ngaphezulu .