Question

我有这样的查询

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

与o / p

temp        t
A1          1

但是如果没有记录，这就是所选日期会发生什么：我没有得到任何结果。答案如A1，A2，A3

我需要这样的o / p

temp   t
A1     1
A2     0
A3     0

Answer 1

你必须做一些自我JOIN技巧来获得每个答案的记录：

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`

请确保您在survey.temp上有索引。

如果没有记录，我如何计算为0？

1 个答案: