首页 \ 问答 \ MySQL查询三个表(MySQL query for three tables)

MySQL查询三个表(MySQL query for three tables)

 我有三个人表，属性和属性的潜在价值。 我无法找出一个查询来显示所有人，每个人属性及其缺失/ null属性。 

 这是一个示例表......  
attributes
+---------------------+
| attribute_name (col)|
+---------------------+
| name                |
+---------------------+
| age                 |
+---------------------+
| gender              |
+---------------------+
| email               |
+---------------------+

people
+-----------+----------+
| person_id | value_id |
+-----------+----------+
| 2         | 7        |
+-----------+----------+
| 2         | 9        |
+-----------+----------+
| 3         | 8        |
+-----------+----------+

values
+---------------+----------------+-------+
| value_id (pk) | attribute_name | value |
+---------------+----------------+-------+
| 7             | age            | 35    |
+---------------+----------------+-------+
| 8             | age            | 28    |
+---------------+----------------+-------+
| 9             | gender         | male  |
+---------------+----------------+-------+
 

 我如何加入这三个表来显示这样的东西？  
+-----------+----------+-----------------+--------+
| person_id | value_id | attribute_name  | value  |
+-----------+----------+-----------------+--------+
| 2         | 7        | age             | 35     |
+-----------+----------+-----------------+--------+
| 2         | 9        | gender          | male   |
+-----------+----------+-----------------+--------+
| 2         | NULL     | name            | NULL   |
+-----------+----------+-----------------+--------+
| 2         | NULL     | email           | NULL   |
+-----------+----------+-----------------+--------+
| 3         | 8        | age             | 28     |
+-----------+----------+-----------------+--------+
| 3         | NULL     | gender          | NULL   |
+-----------+----------+-----------------+--------+
| 3         | NULL     | name            | NULL   |
+-----------+----------+-----------------+--------+
| 3         | NULL     | email           | NULL   |
+-----------+----------+-----------------+--------+

I have three tables with people, the attributes and potential value for the attributes. I can't figure out a query to display all the people, each persons attributes and their missing/null attributes. 

 Here's an example table... 
attributes
+---------------------+
| attribute_name (col)|
+---------------------+
| name                |
+---------------------+
| age                 |
+---------------------+
| gender              |
+---------------------+
| email               |
+---------------------+

people
+-----------+----------+
| person_id | value_id |
+-----------+----------+
| 2         | 7        |
+-----------+----------+
| 2         | 9        |
+-----------+----------+
| 3         | 8        |
+-----------+----------+

values
+---------------+----------------+-------+
| value_id (pk) | attribute_name | value |
+---------------+----------------+-------+
| 7             | age            | 35    |
+---------------+----------------+-------+
| 8             | age            | 28    |
+---------------+----------------+-------+
| 9             | gender         | male  |
+---------------+----------------+-------+
 

 How do I join the three tables to display something like this? 
+-----------+----------+-----------------+--------+
| person_id | value_id | attribute_name  | value  |
+-----------+----------+-----------------+--------+
| 2         | 7        | age             | 35     |
+-----------+----------+-----------------+--------+
| 2         | 9        | gender          | male   |
+-----------+----------+-----------------+--------+
| 2         | NULL     | name            | NULL   |
+-----------+----------+-----------------+--------+
| 2         | NULL     | email           | NULL   |
+-----------+----------+-----------------+--------+
| 3         | 8        | age             | 28     |
+-----------+----------+-----------------+--------+
| 3         | NULL     | gender          | NULL   |
+-----------+----------+-----------------+--------+
| 3         | NULL     | name            | NULL   |
+-----------+----------+-----------------+--------+
| 3         | NULL     | email           | NULL   |
+-----------+----------+-----------------+--------+

原文：https://stackoverflow.com/questions/14674949

更新时间：2024-01-31 21:01

最满意答案

 谢谢，@martync！ 将我的评论作为答案重新发布，因为它实际上已经回答了问题。  
 该文档明确指出“您不能在HTML文档中使用JavaScript来触发打印” ，并提供了如何使用Java API的示例。 Chrome for Android（至少是Beta）支持window.print() 。 

Thanks, @martync! Reposting my comment as an answer, as it has turned out to actually answer the question. 
The documentation explicitly says "You cannot use JavaScript in a HTML document to trigger printing", and provides an example of how to use the Java API. Chrome for Android (at least Beta) supports window.print().

MySQL查询三个表(MySQL query for three tables)

最满意答案

相关问答

需要webview的帮助(need help for webview)[2023-03-01]

通过android webview中的javascript将一些元素附加到html页面(append some element to html page via javascript in android webview)[2023-03-02]

在android webview中使用javascript(Use javascript in an android webview)[2023-02-16]

Swift：使用Swift和JavaScriptCore打印WebView的Html标题(Swift: Print Html title of WebView using Swift And JavaScriptCore)[2022-03-07]

带有HTML按钮和JavaScript的Android WebView(Android WebView with HTML button and JavaScript)[2022-01-15]

Android HTML WebView(Android HTML WebView)[2022-09-26]

Android打印HTML文档(Android Print HTML Document)[2022-06-12]

Android：从WebView打印html文档(Android : Print html document from WebView)[2023-08-28]

Android：创建用于打印的文档(Android: Create document for printing)[2021-11-19]

使用javafx从webview中打印(take print from webview using javafx)[2022-11-17]

相关文章

最新问答