Isikhokelo sokusebenzisana kwangaphakathi kwi-SQL kwiDatha yeDatha kwiTables Multiple

Sebenzisa ii-SQL zangaphakathi zokudibanisa ukudibanisa idatha kwietrafti ezintathu okanye ngaphezulu

Ungasebenzisa izitatimende ze-SQL JOIN ukudibanisa idatha kwietrafti ezintathu okanye ngaphezulu. I-SQL JOIN iguquguquke kakhulu, kwaye ukusebenza kwayo okunamandla kunokusetyenziswa ukudibanisa idatha ukusuka kwiibhile ezininzi. Makhe sijonge kwizitatimenti ze-SQL ezikuvumela ukuba udibanise iziphumo ezivela kwiibhile ezithathu ezahlukeneyo usebenzisa ukujoyina kwangaphakathi.

Ukujoyina kwangaphakathi

Ngokomzekelo, thatha iithebhile eziqukethe abaqhubi kwitheyibhile enye kunye nomdlalo wesibini kwimoto. Ukudibanisa kwangaphakathi kwenzeka apho zombini isithuthi kunye nomqhubi zifumaneka kwisixeko esifanayo. Umgca wangaphakathi ukhetha yonke imigca kwiibhola zombini eziqulethe umdlalo phakathi kwamakholomu eendawo.

Isitatimende se-SQL esingezantsi sidibanisa idatha ukusuka kwiibhola zabaqhubi kunye nezithuthi kwiimeko apho umqhubi kunye nesithuthi sitholakala kwisixeko esifanayo:

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

Lo mbuzo uvelisa iziphumo ezilandelayo:

Igama lomnxeba wokuqala -------- --------- --- Baker Baker H122JM uSmy Michael Michael D824HA Smythe Michael P091YF Jacobs Abraham J291QR Jacobs Abraham L990MT

Ngoku, ukwandisa lo mzekelo ukufaka itafile yesithathu. Cinga ukuba ufuna ukufaka kuphela abaqhubi kunye nezithuthi ezikhoyo kwiindawo ezivulekileyo ngeveki. Unokuzisa itafile yesithathu kumbuzo wakho ngokusula isitatimende se-JOIN ngolu hlobo:

HLOLA igama lokugqibela, igama lomsebenzisi, itekisi, i-open_weekends KWABASEBENZI abaqhubi, izithuthi, indawo. --------- --- ------------- Baker Roland H122JM ewe uYakobi Abraham Abraham J291QR ewe uYakobi Abraham L990MT ewe

Ukongezwa okunamandla kwisitatimende esisiseko se-SQL JOIN kukuvumela ukuba udibanise idatha ngendlela enzima. Ukongeza kokudibanisa iitheyibhile kunye nokudibanisa kwangaphakathi, ungasebenzisa le ndlela ukuhlanganisa iintlanzi ezininzi usebenzisa ukujoyina kwangaphandle. Amaqela angaphandle aquka iziphumo ezikhoyo kwitheyibhile enye kodwa akanalo mdlalo ohambelana netafile edibeneyo.