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關(guān)于SQL 簡單的語法問題,isnull，內(nèi)容太長，具體的情況如下所示

C++ MySQL

慕慕森 2021-05-30 09:06:08

簡單的sql語句,由于自己水平一般,不知道錯在哪里...忘熟悉語句的人指導(dǎo)一二,謝謝!select new_name as 年度,count(new_name) as 總份數(shù),round(sum(case new_q01 when '0' then filterednew_survey.new_q01when filterednew_survey.new_q01 is null then '0'else(filterednew_survey.new_q01-1.00)end),2) as 產(chǎn)品的銷售價格打分from filterednew_surveygroup by new_name為什么這句提示關(guān)鍵字 'is' 附近有語法錯誤???selectnew_name as year,count(new_name) as quantity,round(sum(isnull(new_q01,1.00)-1.00)/sum(casewhen new_q01 is null then 0else 1 end ),2) as 產(chǎn)品的銷售價格打分from filterednew_surveygroup by new_name這句沒有問題.selectnew_name as year,count(new_name) as quantity,round(sum(isnull(new_q01,1.00)-1.00)/sum(casewhen new_q01 is null then 0else 1 end ),2) as 產(chǎn)品的銷售價格打分from filterednew_surveygroup by new_name這句也沒有問題請各位指導(dǎo)下~~~經(jīng)過幾位的幫忙,我自己修改了一下,改成select new_name as 年度,count(new_name) as 總份數(shù),round(sum(case new_q01 when '0' then filterednew_survey.new_q01else (isnull(filterednew_survey.new_q01,1.00)-1.00)end),2) as 產(chǎn)品的銷售價格打分from filterednew_surveygroup by new_name也重新理解了下isnull但是有還是有點小小的不明白selectnew_name as year,count(new_name) as quantity,round(sum(isnull(new_q01,1.00)-1.00)/sum(casewhen new_q01 is null then 0else 1 end ),2) as 產(chǎn)品的銷售價格打分from filterednew_surveygroup by new_name為什么這句的也是is null then 0就可以呢?

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2 回答

慕少森

TA貢獻2019條經(jīng)驗獲得超9個贊

select new_name as 年度,
count(new_name) as 總份數(shù),

round(sum(case isnull(new_q01,0) when '0' then '0'
else(filterednew_survey.new_q01-1.00) end),2) as 產(chǎn)品的銷售價格打分

from filterednew_survey
group by new_name

改成這個試一下

-------------------------------
when new_q01 is null then 0
else 1 end
這個是不行的你會發(fā)現(xiàn) 不管他是不是null 他返回的都是1