組和計數返回SQL

Question

我有兩個表abb和abb_click。

abb包含哪些對象的信息ident這是活動的。 abb_click包含來自每個student_id的信息，關於每個ident。

我 「只是」 想算活躍的ident在abb_click特定student_id數據。下面

的選擇似乎只計算活動IDENT S，不採取任何擔憂，如果IDENT是abb_click。

你可以在這裏看到小提琴：http://sqlfiddle.com/#!9/b7262/1

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結果應該是： 爲student_id數據945 - 2的活性的ident小號

問題：我該怎麼辦「調整「SELECT來計算有效ident s在表abb加入abb_click？

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SELECT t.student_id, number_of_idents 
FROM `abb_click` AS t 
    INNER JOIN 
     (SELECT ident, COUNT(ident) as number_of_idents FROM `abb` AS k 
     WHERE k.active = '1' 
    ) AS t3 
    ON t.ident = t3.ident 
WHERE t.student_id = '945' 
GROUP BY t.student_id 
ORDER BY number_of_idents ASC; 

表abb

bid, ident, active 

表abb_click

kid, ident, student_id, click 

數據表abb

1, 'ma53', 1 
2, 'ma664', 1 
3, 'ma779', 0 
4, 'ma919', 1 

數據表abb_click

1, 'ma53', 945, 'E' 
2, 'ma53', 945, 'E' 
3, 'ma53', 945, 'C' 
4, 'ma664', 945, 'C' 
5, 'ma664', 945, 'A' 
6, 'ma664', 945, 'E' 
7, 'ma779', 945, 'A' 

Answer 1

我相信這應該做你想做的。

select student_id, COUNT(distinct ac.ident) as active_idents 
from abb_click ac 
join abb on abb.ident = ac.ident 
where abb.active = 1 
--and student_id = 945 
group by student_id 

Answer 2

除非我已經錯過，瞭解這應該工作。

SELECT abb.*, COUNT(abb_click.id) as total_abb_clicks 
FROM abb 
INNER JOIN abb_click ON abb_click.ident = abb.ident 
WHERE abb.active = 1 && abb_click.student_id = 945 
GROUP BY abb.id 

- 編輯：抱歉，我忘記了學生的狀況。因此，這應該返回：

投標，IDENT，活躍，total_abb_clicks
1， 'ma53'，1，3
2， 'ma664'，1，3
4， 'ma919'，1,1

Answer 3

可以返回的ident的獨特價值，並通過將它們分組，然後用abb加入和做計數student_id數據：

SELECT click.student_id, COUNT(click.ident) as total_abb_clicks 
FROM abb 
INNER JOIN (select ident, student_id from abb_click group by ident, student_id) click ON click.ident = abb.ident 
WHERE abb.active = 1 and click.student_id=945 
GROUP BY click.student_id