Question

这是我的第一个问题所以我希望我不要搞砸它。

这是我帮助我解释的一个SQL小提琴：http://sqlfiddle.com/#!9/7f2b5c/7

我们有问题，答案，question_types和answer_types。

我想知道每个问题，有多少人回答了每个answer_type以及有多少人回答了这个问题，但是我无法得到总数。

这就是我得到的：

id | fk_question_type | description            | num | value      | total
1  | 1                | How was the breakfast? | 0   | Bad        | 0
1  | 1                | How was the breakfast? | 1   | Good       | 1
1  | 1                | How was the breakfast? | 0   | Indifferent| 0
1  | 1                | How was the breakfast? | 2   | Very good  | 2
2  | 1                | How was the lunch?     | 0   | Bad        | 0
2  | 1                | How was the lunch?     | 1   | Good       | 1
2  | 1                | How was the lunch?     | 0   | Indifferent| 1
2  | 1                | How was the lunch?     | 1   | Very good  | 1

这就是我想要的：

id | fk_question_type | description            | num | value      | total
1  | 1                | How was the breakfast? | 0   | Bad        | 3
1  | 1                | How was the breakfast? | 1   | Good       | 3
1  | 1                | How was the breakfast? | 0   | Indifferent| 3
1  | 1                | How was the breakfast? | 2   | Very good  | 3
2  | 1                | How was the lunch?     | 0   | Bad        | 2
2  | 1                | How was the lunch?     | 1   | Good       | 2
2  | 1                | How was the lunch?     | 0   | Indifferent| 2
2  | 1                | How was the lunch?     | 1   | Very good  | 2

我正在尝试的查询：

SELECT id, fk_question_type, description, num, value, SUM(num) AS totalAnswers
FROM (
    (SELECT q.id, q.fk_question_type, q.description, COUNT(a.id) AS num, at.value
    FROM answer a 
    LEFT JOIN question q ON a.`fk_question`=q.`id` 
    LEFT JOIN answer_type at ON at.id = a.`fk_answer_type` 
    GROUP BY q.id, at.id  ORDER BY q.id, at.id)
    UNION ALL
    (SELECT q.id, q.fk_question_type, q.description, 0 AS num, at.value
    FROM answer a 
    LEFT JOIN question q ON a.`fk_question`=q.`id` 
    LEFT JOIN answer_type at ON at.fk_question_type=q.fk_question_type
    GROUP BY q.id, at.id  ORDER BY q.id, at.id)
) AS T 
WHERE fk_question_type = 1
GROUP BY id, value ORDER BY id

如何在保留其他列的同时对具有相同id的行的num进行求和？

Answer 1

使用子查询获取每个id的总计，并将其与获取每值行的查询相连接。

在外部查询中，您应该使用SUM(num)或MAX(num)来合并num中两个查询的UNION值。

SELECT T.id, fk_question_type, description, SUM(num) AS num, value, T2.totalAnswers
FROM (
    (SELECT q.id, q.fk_question_type, q.description, COUNT(a.id) AS num, at.value
    FROM answer a 
    LEFT JOIN question q ON a.`fk_question`=q.`id` 
    LEFT JOIN answer_type at ON at.id = a.`fk_answer_type` 
    GROUP BY q.id, at.id  ORDER BY q.id, at.id)
    UNION ALL
    (SELECT q.id, q.fk_question_type, q.description, 0 AS num, at.value
    FROM answer a 
    LEFT JOIN question q ON a.`fk_question`=q.`id` 
    LEFT JOIN answer_type at ON at.fk_question_type=q.fk_question_type
    GROUP BY q.id, at.id  ORDER BY q.id, at.id)
) AS T 
JOIN (SELECT q.id, COUNT(*) AS totalAnswers
      FROM answer a 
      LEFT JOIN question q ON a.`fk_question`=q.`id` 
      LEFT JOIN answer_type at ON at.id = a.`fk_answer_type` 
      GROUP BY q.id) AS t2 ON T.id = T2.id
WHERE fk_question_type = 1
GROUP BY T.id, value

DEMO

Mysql查询总结了另一个带有条件的列

1 个答案: