如果沒有記錄，我可以如何計數爲0？

Question

我有這樣

select `temp`, IfNULL(count(id),0) t 
from survey 
where `temp`<>'NULL' and `temp`<> '' and date(submitdate)='date' 
group by `temp 

與O/P查詢

temp  t 
A1   1 

但這裏是在選定的日期會發生什麼，如果沒有記錄：我沒有得到任何結果。答案是像A1，A2，A3

我需要這樣的

temp t 
A1  1 
A2  0 
A3  0 

Answer 1

O/P你將不得不做一些自我JOIN過關獲得每一個答案記錄：

SELECT s.`temp`, count(survey.id) t 
-- This will ensure that you will get all relevant answers A1, A2, A3 
FROM (
    SELECT DISTINCT `temp` 
    FROM survey 
    WHERE `temp` <> 'NULL' and `temp` <> '' 
--    ^^^^^^^^^ Might want to replace this by `temp` IS NOT NULL? 
) s 
-- Only then, you will actually get the actual records per answer and date 
LEFT OUTER JOIN survey 
    ON s.`temp` = survey.`temp` 
    AND date(survey.submitdate) = 'date' 
GROUP BY s.`temp` 

只要確保您有survey.temp的索引。