sqlserver中case when用法Case具有兩種格式簡單函數(shù)和搜索

CaseCaseCase--CaseCASEWHEN'1THEN男'WHEN'2THEN女'ELSE'其他'END--CaseCASEWHEN='1'THEN'男'WHEN='2'THEN'女'ELSE其他還有一個(gè)需要注意的問題，CaseCase部分將會被CASEWHENcol_1INabTHEN第一類WHENcol_1INaTHEN第二類ELSE'其他國家（country）（population）中國600100100英國法國250德國墨西哥250洲人口亞洲洲其他Case函數(shù)，SQL代碼如下SELECTSUM(population),CASEcountryWHEN中國THEN亞洲WHEN''THEN'亞洲'WHEN''THEN'亞洲'WHEN''THEN'洲'WHEN''THEN'洲'WHEN'墨西哥'THEN'洲'ELSE'其他'ENDFROMGROUPBYCASEcountryWHEN'中國'THEN'亞洲'WHEN''THEN'亞洲'WHEN''THEN'亞洲'WHEN''THEN'洲'WHEN''THEN'洲'WHEN'墨西哥'THEN'洲'ELSE'其他'END;同樣的，我們也可以用這個(gè)方法來判斷工資的等級，并統(tǒng)計(jì)每一等級的人數(shù)。SQL代碼如CASEWHENsalary<=500THENWHENsalary>500ANDsalary<=600THEN'2'WHENsalary>600ANDsalary<=800THEN'3'WHENsalary>800ANDsalary<=1000THEN'4'ELSENULLENDsalary_class,GROUPBYCASEWHENsalary<=500THENWHENsalary>500ANDsalary<=600THEN'2'WHENsalary>600ANDsalary<=800THEN'3'WHENsalary>800ANDsalary<=1000THEN'4'ELSENULLEND;SQL國家（country）（）人口（population）255151249英國1英國2國家男女中國34045555149英國40UNION也可以實(shí)現(xiàn)用一條語句進(jìn)行查詢。但是那樣增加消耗(SELECTSUM(CASEWHEN='1'populationELSE0END),--人SUM(CASEWHEN='2'populationELSE0END)女性人口FROMTable_AGROUPBYCheckCaseCheckCase函數(shù)在很多情況下都是非常不錯(cuò)的解決方法?？赡苡泻芏嗳烁揪筒籆heckSQLCheck。CONSTRAINTcheck_salaryCHECK(CASEWHEN='2'THENCASEWHENsalary>1000THEN1ELSE0ENDELSE1END=1Check，如下所示CONSTRAINTcheck_salaryCHECK(='2'ANDsalary>1000) 請 .aspxempnameempcodekinddays714204事假9714271加班271427962empnameempcodekinddays714204事假90714271事假027142790714207產(chǎn)假病假0721338病假20721338事假0368selectempnamecasewhenkind='加班then事假'elsekindend'kind'