使用具有多个表连接的聚合函数的问题

Question

我的目标是创建一个聚合函数（总和）并对元素进行分组，但出现错误，

这是我完成的所有步骤

1-第一步 进行编码

SELECT ca.question_id , ca.choice_0 ,ca.choice_1 ,ca.choice_2 ,ca.choice_3 ,ca.choice_4 ,q.headline_id  FROM closed_answers ca
                INNER JOIN questions q ON ca.question_id = q.id 
                INNER JOIN headline h ON q.headline_id = h.id
                INNER JOIN forms f ON h.form_id = f.id
                WHERE f.id = 2

对结果

http://img717.imageshack.us/img717/685/firststep.png

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2-现在我想聚合选择并按标题 id 对它们进行分组，但是当我编写时，

SELECT sum(ca.choice_0) ,sum(ca.choice_1) ,sum(ca.choice_2) ,sum(ca.choice_3) ,sum(ca.choice_4) ,q.headline_id  FROM closed_answers ca

                INNER JOIN questions q ON ca.question_id = q.id 
                INNER JOIN headline h ON q.headline_id = h.id
                INNER JOIN forms f ON h.form_id = f.id
                GROUP BY q.headline_id
                WHERE f.id = 2

错误是

A Database Error Occurred

Error Number: 1064

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE f.id = 2' at line 6

SELECT sum(ca.choice_0) ,sum(ca.choice_1) ,sum(ca.choice_2) ,sum(ca.choice_3) ,sum(ca.choice_4) ,q.headline_id FROM closed_answers ca INNER JOIN questions q ON ca.question_id = q.id INNER JOIN headline h ON q.headline_id = h.id INNER JOIN forms f ON h.form_id = f.id GROUP BY q.headline_id WHERE f.id = 2

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PS：当我按关键字删除分组并对所有选择求和时，它会起作用

http://img203.imageshack.us/img203/8186/secondstepx.png

Answer 1

将GROUP BY 放在WHERE 之后。