如何做MySQL加入并使用PHP来获取值

Question

我正在尝试编写一个mysql查询来以这种格式提取数据：

<table>
    <caption>table title and/or explanatory text</caption>
    <thead>
        <tr>
            <th>User ID</th>
            <th>First Name</th>
            <th>Last Name</th>
            <th>Field Name 1</th>
            <th>Field Name 2</th>
            <th>Field Name 3</th>
            <th>Field Name 4</th>
            <th>Field Name 5</th>
        </tr>
    </thead>
    <tbody>
    <?php 

        while ($row = mysqli_fetch_array($query)) {

        echo "<tr>
                <td>" .$row{'user_id'}. "</td>
                <td>" .$row{'first_name'}. "</td>
                <td>" .$row{'last_name'}. "</td>
                <td>" .$row{'field_name_1'}. "</td>
                <td>" .$row{'field_name_2'}. "</td>
                <td>" .$row{'field_name_3'}. "</td>
                <td>" .$row{'field_name_4'}. "</td>
                <td>" .$row{'field_name_5'}. "</td>
            </tr>";
        }
    ?>
    </tbody>
</table>

数据库中的表格格式如下。

表：user_data

user_id      |     first_name     |    last_name     |
------------------------------------------------------
1            |     Jeff           |    Smith         |
------------------------------------------------------
2            |     Bob            |    Smith         |
------------------------------------------------------
3            |     Steve          |    Smith         |
------------------------------------------------------
4            |     Mary           |    Smith         |
------------------------------------------------------
5            |     Anna           |    Smith         |
------------------------------------------------------

表：custom_fields

custom_field_id   |    name         |
-------------------------------------
3                 |    field name   |
-------------------------------------
5                 |    field name   |
-------------------------------------
7                 |    field name   |
-------------------------------------
9                 |    field name   |
-------------------------------------
11                |    field name   |
-------------------------------------

表：custom_field_data

user_id      |     custom_field_id    |    value     |
------------------------------------------------------
1            |     3                  |    XXXX      |
------------------------------------------------------
1            |     5                  |    BBBB      |
------------------------------------------------------
1            |     7                  |    CCCC      |
------------------------------------------------------
1            |     9                  |    ZZZZ      |
------------------------------------------------------
1            |     11                 |    YYYY      |
------------------------------------------------------
2            |     3                  |    XXXX      |
------------------------------------------------------
2            |     5                  |    BBBB      |
------------------------------------------------------
2            |     7                  |    CCCC      |
------------------------------------------------------
2            |     9                  |    ZZZZ      |
------------------------------------------------------
3            |     3                  |    XXXX      |
------------------------------------------------------
3            |     5                  |    BBBB      |
------------------------------------------------------
3            |     9                  |    ZZZZ      |
------------------------------------------------------
3            |     11                 |    YYYY      |
------------------------------------------------------

我正在寻找查询数据然后使用PHP或AJAX将其打印到屏幕的最佳解决方案。 这可能吗？ 使用json会更好吗？ 一个示例查询会很棒。

仅供参考：从长远来看，所有提取的数据都需要在屏幕上进行过滤。 谢谢您的帮助。

我想要的输出是

user_id      |     first_name     |    last_name     |  custom_field_3  |   custom_field_5  |   custom_field_7  |   custom_field_9  |   custom_field_11     |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
1            |     Jeff           |    Smith         |  XXXX            |   BBBB            |   CCCC            |   ZZZZ            |   YYYY                |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
2            |     Bob            |    Smith         |  XXXX            |   BBBB            |   CCCC            |   ZZZZ            |   YYYY                |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
3            |     Steve          |    Smith         |  XXXX            |   BBBB            |   CCCC            |   ZZZZ            |   YYYY                |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
4            |     Mary           |    Smith         |  XXXX            |   BBBB            |   CCCC            |   ZZZZ            |   YYYY                |
-------------------------------------------------------------------------------------------------------------------------------------------------------------
5            |     Anna           |    Smith         |  XXXX            |   BBBB            |   CCCC            |   ZZZZ            |   YYYY                |
-------------------------------------------------------------------------------------------------------------------------------------------------------------

Answer 1

您可以使用group_concat函数https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat与我之前的查询来获取每个用户的单条记录。 。

如果你有一个SQLfiddle我可以测试它，但因为我没有任何数据要测试...

select ud.firstname, ud.lastname, group_concat(cf.name) 
from user_data as ud 
join custom_field_data as cfd 
on cfd.user_id = ud.user_id 
join custom_fields as cf 
on cf.custom_field_id = cfd.custom_field_id

我在3个表上测试了这个，我有类似的设置，所以我认为它应该工作; 名称可能需要调整。

更新：

select ud.firstname, ud.lastname, group_concat(cf.name) 
from user_data as ud 
join custom_field_data as cfd 
on cfd.user_id = ud.user_id 
join custom_fields as cf 
on cf.custom_field_id = cfd.custom_field_id
group by ud.user_id

Answer 2

让我们从custom_field_data到user_data表的简单连接开始，其中值和字段名称是硬编码的：

SELECT 
 u.*,
 f1.value as "<Field 1 Name>",
 ...
 f2.value as "<Field N Name>"
FROM 
 user_data u LEFT JOIN 
 custom_field_data f1 ON u.user_id = f1.user_id AND f1.custom_field_id = 1
 LEFT JOIN
 custom_field_data f ON u.user_id = fn.user_id AND fn.custom_field_id = <N>

现在，如果要在不进行硬编码的情况下提取数据，则需要根据custom_fields表中的数据动态构建SQL：

SELECT * FROM custom_fields;

如果您的某些自定义字段从未与用户相关，则您希望限制自定义字段的数量，如下所示：

SELECT * FROM custom_fields f
WHERE EXISTS 
       (SELECT * FROM custom_field_data 
        WHERE f.custom_field_id = custom_field_id)

最后，要在PHP中构建所需的SQL，您需要以下字符串部分：

// Begin SELECT clause (static):
$sql = "SELECT u.*,"

// Add all fields that you selected form the custom_fields:
foreach ($result as $row) { // Don't forget to handle commas
  $sql = $sql + <expression that gets codes and name>
}

// Start FROM clause (static):
$sql = $sql + " FROM user_data u "


// Join to custom_field_data:
foreach ($result as $row) {
  $sql = $sql + " LEFT JOIN custom_field_data <alias expression> ON ..
}

最后，您应该获得一个带有SQL的字符串，该字符串将用户连接到每个可用自定义字段的custom_field_data 。

Answer 3

可以使用$.ajax()和PHP提取数据。 创建一个文件data.php我们将用ajax加载这个文件。 在data.php文件中编写此代码。

$query = mysqli_query("select * from custom_field_data 
         inner join 
         user_data on user_data.user_id = custom_field_data.user_id
         inner join 
         custom_fields on custom_field_data.custom_field_id = custom_fields.custom_field_id");
<table>
<caption>table title and/or explanatory text</caption>
<thead>
    <tr>
        <th>User ID</th>
        <th>First Name</th>
        <th>Last Name</th>
        <th>Field Name 1</th>
        <th>Field Name 2</th>
        <th>Field Name 3</th>
        <th>Field Name 4</th>
        <th>Field Name 5</th>
    </tr>
</thead>
<tbody>
 <?php 

    while ($row = mysqli_fetch_array($query)) {

    echo "<tr>
            <td>" .$row{'user_id'}. "</td>
            <td>" .$row{'first_name'}. "</td>
            <td>" .$row{'last_name'}. "</td>
            <td>" .$row{'field_name_1'}. "</td>
            <td>" .$row{'field_name_2'}. "</td>
            <td>" .$row{'field_name_3'}. "</td>
            <td>" .$row{'field_name_4'}. "</td>
            <td>" .$row{'field_name_5'}. "</td>
        </tr>";
    }
?>
</tbody>

在主页面中使用button加载数据。

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
 <script type="text/javascript">
$(function(){
    $('#load-data').click(function(){
        $.post('data.php', function(data){
            $('#results').html(data);
        });
    });
});
</script>

在sqlfiddle上的例子

Answer 4

我认为最好的方法是使用join，因为它会减少DB和PHP之间传输的数据大小

您可以使用JSON，因为它很轻。

您可以将事物隐藏在隐藏字段中，并将其用于完全在客户端进行进一步过滤

更新 -

对于Sql server我会写这样的查询

select 
  t1.user_name,
  t1.first_name,
  t1.last_name,
  (select name from custom_fields 
   where custom_field_id= t2.custom_field_id) 
from
 user_data t1 left join
 custom_field_data t2 on t1.user_id=t2.userid

根据my-sql改变它