Yintoni eyenza umsebenzi SQL CONCAT?

Ukusebenza edatha uhlala unxulunyaniswa ekufumaneni iziphumo umbuzo. Kwaye kwezinye iimeko, olu lwazi kufuneka kuziwe ikhusi ngendlela ethile okanye ukudibanisa kunye nezinye iinkcukacha. Ukusombulula le ngxaki kukho umsebenzi SQL - CONCAT.

Yintoni eyenza umsebenzi CONCAT?

Xa usenza umsebenzi ezithile iinkcukacha, kukho imfuneko kubanjiswene lines iinkcukacha ezongezelelweyo okanye phakathi kwabo. Ukusombulula le ngxaki kukho umsebenzi SQL - CONCAT. Xa usebenzisa oko imigca emibini okanye ngaphezulu uya zadityaniswa omnye. Kulo msebenzi concatenation lwenziwa ngokuchanekileyo njengoko ngomtya, kunye variables ngamanani.

Kwezinye iinkcukacha, SQL CONCAT uye iintlobo eziliqela. Umzekelo, I SQL yam iye woogxa balo - CONCAT_WS. Umahluko phakathi kwemisebenzi engabalulekanga: kwimeko yokuqala, xa idityaniswe argument ixabiso kabani na byte, ngesiphumo concatenation alisebenzi, kwaye usebenzisa ngobuwena yesibini edibanisa we- zero ukuba nidlobe nje.

umsebenzi syntax

Xa usebenzisa umsebenzi CONCAT, SQL-kwezivakalisi kufuna wenkqubo ukusebenzisa kwiimpikiswano ngokulandelelana apho operands zezi ixakathwe ke. Sam imisebenzi string concatenation kwezivakalisi abamaziyo ilula: emva CONCAT igama elikwizibiyeli, wodwa ngeziphumlisi ukubonisa zonke iingxoxo eziyimfuneko okanye imiqolo ukuze, yaye emva ipharenthesis wokuvala, ukuba kuyimfuneko, bonisa AS elingundoqo kunye negama variable apho iziphumo ziya kurekhodwa. CONCAT umsebenzi template ngolu hlobo lulandelayo:

CONCAT (string1, string2 [, umgca 3, ...]) [AS var_name].

Kufuneka kuqatshelwe ukuba njengoko iingxoxo lomsebenzi ingasetyenziswa njengento we- kunye umtya imilinganiselo lwamanani, yaye umsebenzi ubuyisela yoko. Umzekelo, ukusebenza SQL CONCAT ngokwayo. Ngenxa yoko, umsebenzi siseko isekela ezazihlala.

Indlela yokwenza ngaphandle kokusebenzisa CONCAT?

Kwimeko apho kukho imfuneko yokuba kwenziwe ngaphandle kokusebenzisa kotyando, okanye wenkqubo ngumsebenzi CONCAT ayaziwa, i-SQL inikeza lobeko enye ngaphezulu intambo concatenation. Ukuze wenze oku, sebenzisa "+" umqhubi, kodwa le ndlela iye eziliqela iimpawu ekufuneka ithathelwe ingqalelo xa besebenza kunye naye.

Xa usebenzisa "+" ukuba operands amaxabiso ngamanani, iziphumo msebenzi uya kuba Ukongeza eziqhelekileyo amanani, kunye esinokudibanisa manani umgca ngaphandle inkqubo yengxoxo yokubana iya kubuyela impazamo xa kuyimfuneko. Ngoko, xa umbuzo japan elilandelayo ixabiso "6":

KHETHA 1 + 2 + 3.

Kungenjalo zombini iindlela ncam ndibuyele isiphumo esifanayo.