使用嵌套格式分组 Mysql 查询

Question

我已经搜索过旧线程，但还没有找到以下问题的解决方案：是否可以在不使用嵌套查询的情况下对 mysql 结果进行分组和排列？

请参阅下面的示例。

我有：

Month Jan, Location USA, Program DDD
Month Jan, Location UK, Program EEE
Month Jan, Location USA, Program LLL
Month FEB, Location UAE, Program EEE
Month FEB, Location USA, Program DDD
Month FEB, Location UK, Program MMM
Month MAR, Location USA, Program FFF
Month MAR, Location UAE, Program FFF
Month MAR, Location UK, Program FFF

我希望它们像这样显示：

                +---------++---------++---------+
                |Month Jan||Month Feb||Month Mar|
+---------------+---------++---------++---------+
|Location USA   |         ||         ||         |
+---------------+---------++---------++---------+
|               |DDD      ||DDD      ||FFF      |
+---------------+---------++---------++---------+
|               |EEE      ||         ||         |
+---------------+---------++---------++---------+
|               |LLL      ||         ||         |
+---------------+---------++---------++---------+
|Location UK    |         ||         ||         |
+---------------+---------++---------++---------+
|               |EEE      ||MMM      ||FFF      |
+---------------+---------++---------++---------+
|Location UAE   |         ||         ||         |
+---------------+---------++---------++---------+
|               |         ||EEE      ||FFF      |
+---------------+---------++---------++---------+

我已尝试对查询进行分组，但无法将其呈现到 HTML 表中。

SELECT 
    event.`event_id`,
    event.`event_program_id`,
    event.`event_month`, 
    event.`event_location_id`,
    location.`location_name`,
    program.`program_name`,
    program.`program_shortname`
FROM 
    `event`
LEFT JOIN
    `location`
ON
    event.`event_location_id` = location.`location_id`
LEFT JOIN
    `program`
ON
    event.`event_program_id` = program.`program_id`;

现在它的列表是这样的：

    column1 column2 column3
line1   34              
line2   34              
line3           34  
line5       34          

我想要这样的地方：

    column1 column2 column3 
line1   34      34
                34      34
                34        

line2   34
        34      34      34              
line3           34      
line5       34          

Answer 1

如果您在预期结果中有预定义的列数，例如一年中的几个月，您可以为每一列执行一些内部查询。

我对使用这样的子查询的基于 SQL 的报告有一些经验，最终，这个解决方案管理起来很痛苦:) 今天我只是读取数据，存储在内存中的矩阵中，然后最后根据矩阵生成结果，以后更容易改变。

干杯！

这是一个 PHP 示例

<pre>
<?php
$columns = array();
$data = array();

// add the data from the database
$data["line1"]["column1"] += 34;
$data["line2"]["column1"] += 34;
$data["line3"]["column4"] += 34;
$data["line5"]["column2"] += 34;

$data["line1"]["column1"] += 34;
$data["line3"]["column4"] += 34;

// find the columns
foreach ($data as $line => $column) {
    foreach ($column as $cname => $value) {
        if( ! in_array($cname, $columns) ){
            $columns[] = $cname;
        }
    }
}

sort($columns);

// display column names
echo " \t";
foreach ($columns as $index => $cname) {
    echo $cname . "\t";
}
echo "\n";

// display the data
foreach ($data as $line => $column) {
    echo $line . "\t";
    foreach ($columns as $index => $cname) {
        echo $column[$cname] . "\t";
    }
    echo "\n";
}
?>
</pre>

这是解决问题的另一种方法

<pre>
<?php
$columns = array();
$data = array();

// add the data from the database
// sort the data in the SQL
$data[] = array("l" => "line1", "c"=> "column1", "v" => "AAA");
$data[] = array("l" => "line1", "c"=> "column1", "v" => "BBB");
$data[] = array("l" => "line1", "c"=> "column3", "v" => "CCC");
$data[] = array("l" => "line2", "c"=> "column2", "v" => "AAA");
$data[] = array("l" => "line3", "c"=> "column2", "v" => "AAA");

// find the columns
foreach ($data as $line => $column) {
    if( ! in_array($column["c"], $columns) ){
        $columns[] = $column["c"];
    }
}

sort($columns);

// display column names
echo " \t";
foreach ($columns as $index => $cname) {
    echo $cname . "\t";
}
echo "\n";

$name = '';
$count = 0;
// display the data
foreach ($data as $line => $column) {
    if( $column['l'] == $name ){
        $count ++;
    } else {
        $name = $column['l'];
        $count = 0;
    }

    if( $count == 0 ){
        echo $name . "\t";
    } else {
        echo " \t";
    }   

    foreach ($columns as $index => $cname) {
        if( $column['c'] == $cname ){
            echo $column['v'] . "\t";       
        } else {
            echo " \t";
        }
    }
    echo "\n";
}
?>
</pre>

使用 html 作为输出的其他参考

<table border="1">
<?php
$columns = array();
$data = array();

// add the data from the database
// sort the data in the SQL
$data[] = array("l" => "line1", "c"=> "column1", "v" => "AAA");
$data[] = array("l" => "line1", "c"=> "column1", "v" => "BBB");
$data[] = array("l" => "line1", "c"=> "column3", "v" => "CCC");
$data[] = array("l" => "line2", "c"=> "column2", "v" => "AAA");
$data[] = array("l" => "line3", "c"=> "column2", "v" => "AAA");

// find the columns
foreach ($data as $line => $column) {
    if( ! in_array($column["c"], $columns) ){
        $columns[] = $column["c"];
    }
}

sort($columns);

// display column names
echo "<tr>";
echo "<td>&nbsp;</td>";
foreach ($columns as $index => $cname) {
    echo "<td>".$cname."</td>";
}
echo "</tr>";

$name = '';
$count = 0;
// display the data
foreach ($data as $line => $column) {
    echo "<tr>";

    if( $column['l'] == $name ){
        $count ++;
    } else {
        $name = $column['l'];
        $count = 0;
    }

    if( $count == 0 ){
        echo "<td>".$name."</td>";
    } else {
        echo "<td>&nbsp;</td>";
    }   

    foreach ($columns as $index => $cname) {
        if( $column['c'] == $cname ){
            echo "<td>".$column['v']."</td>";
        } else {
            echo "<td>&nbsp;</td>";
        }
    }
    echo "</tr>";
}
?>
</table>