MySQL查询，从而获得所需的输出

我正在用我的当前查询获得：MySQL查询，从而获得所需的输出

+---------------+--------------------+-------+--------+--------+ 
| Name  |  email  | Apple | Orange | Banana | 
+---------------+--------------------+-------+--------+--------+ 
| NULL   | NULL    | YES | YES | YES | 
| Molly Weasley | [email protected] | YES | YES | YES | 
| Viktor Krum | [email protected] | YES | YES | NULL | 
+---------------+--------------------+-------+--------+--------+

我想要什么：

+---------------+--------------------+-------+--------+--------+--------------+ 
| Name  |  email  | Apple | Orange | Banana | Info Entered | 
+---------------+--------------------+-------+--------+--------+--------------+ 
| Severus Snape | [email protected] |  |  |  | No   | 
| Molly Weasley | [email protected] | YES | YES | YES | Yes   | 
| Viktor Krum | [email protected] | YES | YES |  | Yes   | 
+---------------+--------------------+-------+--------+--------+--------------+

基本上，西弗勒斯·斯内普没有回答问卷，但（他有答案表中没有记录），但我仍然希望向他展示他（因为他收到问卷表中所示的问卷）。苹果，橘子和香蕉对他来说是空白的（由于某种原因它一直显示为YES）。

我使用的查询：

SELECT CONCAT(people.firstName, ' ', people.lastName) AS Name, 
people.email, 
MAX(CASE WHEN questions.fruit = 'apple' THEN 'YES' END) AS Apple, 
MAX(CASE WHEN questions.fruit = 'orange' THEN 'YES' END) AS Orange, 
MAX(CASE WHEN questions.fruit = 'banana' THEN 'YES' END) AS Banana 
FROM answers 
LEFT JOIN questions ON answers.questionID = questions.questionID 
LEFT JOIN people ON questions.person = people.person AND questions.questionnaire = '24' 
GROUP BY CONCAT(people.firstName, ' ', people.lastName), people.email 
ORDER BY Name

的样本数据：

人表：

+-----------+----------+--------------------+--------+ 
| firstName | lastName |  email  | person | 
+-----------+----------+--------------------+--------+ 
| Harry  | Potter | [email protected] |  1 | 
| Ron  | Weasley | [email protected] |  2 | 
| Hermione | Granger | [email protected] |  3 | 
| Severus | Snape | [email protected] |  4 | 
| Viktor | Krum  | [email protected] |  5 | 
| Molly  | Weasley | [email protected] |  6 | 
| Oliver | Wood  | [email protected] |  7 | 
| Remus  | Loopin | [email protected] |  8 | 
+-----------+----------+--------------------+--------+

问表：

+---------------+--------+------------+--------+ 
| questionnaire | person | questionID | fruit | 
+---------------+--------+------------+--------+ 
|   23 |  1 |   55 | apple | 
|   23 |  1 |   56 | orange | 
|   23 |  1 |   57 | banana | 
|   23 |  2 |   58 | apple | 
|   23 |  2 |   59 | orange | 
|   23 |  2 |   60 | banana | 
|   23 |  3 |   61 | apple | 
|   23 |  3 |   62 | orange | 
|   23 |  3 |   63 | banana | 
|   24 |  4 |   64 | apple | 
|   24 |  4 |   65 | orange | 
|   24 |  4 |   66 | banana | 
|   24 |  5 |   67 | apple | 
|   24 |  5 |   68 | orange | 
|   24 |  5 |   69 | banana | 
|   24 |  6 |   70 | apple | 
|   24 |  6 |   71 | orange | 
|   24 |  6 |   72 | banana | 
+---------------+--------+------------+--------+

答案表：

+----------+------------+---------------------+-----------------+ 
| answerID | questionID |  info   | dateAnswered | 
+----------+------------+---------------------+-----------------+ 
|  40 |   59 | some info here  | 5/26/2017 19:23 | 
|  41 |   59 |      | 5/26/2017 18:30 | 
|  42 |   59 |      | 5/26/2017 18:29 | 
|  43 |   66 |      | 5/26/2017 18:36 | 
|  44 |   66 |      | 5/26/2017 20:28 | 
|  45 |   70 |      | 5/26/2017 20:28 | 
|  46 |   55 | more info here  | 5/26/2017 20:29 | 
|  47 |   71 |      | 5/26/2017 20:29 | 
|  48 |   67 |      | 5/26/2017 20:31 | 
|  49 |   64 |      | 5/26/2017 18:37 | 
|  50 |   55 |      | 5/26/2017 18:46 | 
|  51 |   72 |      | 5/26/2017 18:46 | 
|  52 |   72 | another bit of info | 5/26/2017 18:46 | 
|  53 |   72 | and more info  | 5/26/2017 18:46 | 
|  54 |   61 |      | 5/26/2017 18:29 | 
|  55 |   61 |      | 5/26/2017 18:30 | 
|  56 |   68 | the info   | 5/26/2017 18:36 | 
|  57 |   59 |      | 5/26/2017 19:22 | 
|  58 |   66 |      | 5/26/2017 19:37 | 
|  59 |   61 |      | 5/26/2017 19:37 | 
|  60 |   61 |      | 5/26/2017 18:33 | 
|  61 |   68 | this info   | 5/26/2017 18:38 | 
|  62 |   68 |      | 5/26/2017 19:33 | 
|  63 |   68 | some more info  | 5/26/2017 19:42 | 
|  64 |   68 |      | 5/26/2017 19:56 | 
|  65 |   60 |      | 5/26/2017 20:03 | 
+----------+------------+---------------------+-----------------+

来源

2017-06-06 Just a Sec User

尝试更改顺序：

SELECT 
    CONCAT(people.firstName, ' ', people.lastName) AS Name, 
    people.email, 
    MAX(CASE WHEN questions.fruit = 'apple' AND answers.questionID IS NOT NULL THEN 'YES' END) AS Apple, 
    MAX(CASE WHEN questions.fruit = 'orange' AND answers.questionID IS NOT NULL THEN 'YES' END) AS Orange, 
    MAX(CASE WHEN questions.fruit = 'banana' AND answers.questionID IS NOT NULL THEN 'YES' END) AS Banana 
FROM people 
JOIN questions ON questions.person = people.person AND questions.questionnaire = '24' 
LEFT JOIN answers ON answers.questionID = questions.questionID 
GROUP BY CONCAT(people.firstName, ' ', people.lastName), people.email 
ORDER BY Name

来源

2017-06-06 04:56:10 FieryCat

返回* *每个人都从“人”表时，我只想要回人谁收到的调查问卷。在问卷24的情况下，这将是Severus，Viktor和Molly。在Severus应该是空白的时候，Severus，Viktor和Molly的这个查询也是全面的，Viktor应该是空白的香蕉。 –

然后移除问题第一个'LEFT JOIN'（我已经更新了答案） – FieryCat

我不知道我的理解。如果我删除了这一行比我不再包括问表也不再提及“调查问卷24' ，我也失去了什么，答案实际上指的是数据的问题表必须被包括在内。 –

MySQL查询，从而获得所需的输出

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