查詢和組

Question

我有一些會議日期和時間和考官，在這些會議上，我把一個候選人。考生必須通過考試。

我有一個這樣的表：

Exam | Meeting | Niche | Date  | Hour | Examinator | idCandidate 
Math | 1 | 1 |2014-06-28|08:00 | John |  1 
Math | 1 | 2 |2014-06-28|08:20 | John |  0 
Math | 5 | 3 |2014-06-28|13:00 | John |  0 
Math | 2 | 4 |2014-06-28|08:00 | Will |  0 
Math | 2 | 5 |2014-06-28|08:20 | Will |  0 
Math | 3 | 6 |2014-06-29|08:00 | John |  11 
Math | 3 | 7 |2014-06-29|08:20 | John |  0 
Math | 6 | 8 |2014-06-29|14:00 | John |  0 
Bio | 4 | 9 |2014-06-28|08:00 | Bruce |  0 
Bio | 4 | 10 |2014-06-28|08:20 | Bruce |  0 
Bio | 4 | 11 |2014-06-28|08:40 | Bruce |  0 

什麼，我想的是：

Exam | Date | Examinator | Nb Free Candidate 
Math |2014-06-28| John  |   2 
Math |2014-06-28| Will  |   2 
Math |2014-06-29| John  |   2 
Bio |2014-06-28| Bruce  |   3 

其實，我想顯示免費利基（會議）爲了通過考試的編號，日期和審查員。

你能幫我嗎？

Answer 1

你可能在找這個GROUP BY查詢：

SELECT Exam, `Date`, Examinator, COUNT(*) AS nb_free_candidate 
FROM tablename 
WHERE idCandidate = 0 
GROUP BY Exam, `Date`, Examinator 

如果日期列包含日期和時間，你應該使用這樣的：

SELECT Exam, DATE(`Date`), Examinator, COUNT(*) AS nb_free_candidate 
FROM tablename 
WHERE idCandidate = 0 
GROUP BY Exam, DATE(`Date`), Examinator