分組並計數返回的SQL

Question

我有兩個表abb和abb_click 。

abb包含哪個對象標識處於活動狀態的信息。 abb_click包含來自每個student_id的有關每個標識的信息 。

我“只是”想要為特定的student_id計算abb_click的活動身份 。

下面的SELECT似乎只對活動的ident進行計數，如果該標識符位於abb_click中，則abb_click 。

您可以在這里看到小提琴： http ://sqlfiddle.com/#!9/ b7262/1

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結果應為：對於student_id 945-2有效ident s

問題：如何“調整” SELECT來計算與abb_click表abb的活動標識 s？

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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

數據到表abb

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

數據到表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

除非我錯過了理解，否則這應該可行。

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：對不起，我忘記了學生條件。 所以這應該返回：

出價，身份，有效，total_abb_clicks
1，'ma53'，1，3
2，'ma664'，1，3
4，'ma919'，1，1

Answer 2

我相信這應該做您想要的。

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 3

您可以將ident和student_id的不同值分組，然后與abb並進行計數，以返回它們的不同值：

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