带百分比的列表

Question

我正在尝试做出测试答案的百分比。

我有MySQL数据库与测试问题

id | name  | test_id 
---+------------+-------- 
1 | question 1 | 1 
2 | question 2 | 1 
3 | question 3 | 1 
4 | question 4 | 1 
5 | question 1 | 2 
6 | question 2 | 2 
7 | question 3 | 2 
8 | question 4 | 2 

表answers，我把所有的答案，从测试3个表

表tests

id | name 
---+-------- 
1 | test 1 
2 | test 2 

表questions

id | question_id 
---+------------- 
1 | 1 
2 | 2 
3 | 5 
4 | 6 
5 | 7 
6 | 8 

如何在测试中获得已完成问题百分比的列表。在这种情况下是这样的：

name | percentage 
-------+----------- 
test 1 | 50 
test 2 | 100 

Answer 1

尝试

select t.name, 
     cast((count(a.id)/count(q.id)) * 100 as unsigned) as percentage 
from tests t 
left outer join questions q on q.test_id = t.id 
left outer join answers a on a.question_id = q.id 
group by t.name 

请参见本SQLFiddle例如