Question

我从mysql select dynamic row values as column names, another column as value找到了我的问题的答案。这是SQL：

SELECT CONCAT(
  'SELECT dm_generics.dm_id', GROUP_CONCAT(CONCAT('
     ,    t_', REPLACE(field_name, '', ''), '.field_value
         AS ', REPLACE(field_name, '', ''), ''
   ) SEPARATOR ''),
 ' FROM dm_generics ', GROUP_CONCAT(CONCAT('
     LEFT JOIN dm_generics   AS t_', REPLACE(field_name, '', ''), '
            ON dm_generics.dm_id = t_', REPLACE(field_name, '', ''), '.dm_id
           AND t_', REPLACE(field_name, '', ''), '.field_name = ', QUOTE(field_name)
   ) SEPARATOR ''),
 ' GROUP BY dm_generics.dm_id'
) INTO @qry FROM (SELECT DISTINCT field_name FROM dm_generics) t;
PREPARE stmt FROM @qry;
EXECUTE stmt;

但是，我很困惑如何在PDO中执行该查询。

我曾试图使用这样的东西：

$stmt = $dbh->prepare($sql);
if($stmt->execute())
{
    $object = $stmt->fetchAll(PDO::FETCH_OBJ);
    return $object;
}

我没有使用PDO :: prepare，而是尝试使用PDO查询

$stmt = $dbh->query($sql);

但是，我有一个空数组或null。我猜这个查询有些“错误”，也许是因为里面有一个MySQL变量？

以下是答案http://sqlfiddle.com/#!2/6e689/1

提供的小提琴

那么，您能否告诉我问题是什么以及如何使其发挥作用？

更新

作为Your Common Sense建议，现在我可以使这些查询起作用。这是代码：

$sql    = "SELECT CONCAT(
'SELECT dm_generics.dm_id', GROUP_CONCAT(CONCAT('
     ,    t_', REPLACE(field_name, '', ''), '.field_value
         AS ', REPLACE(field_name, '', ''), ''
   ) SEPARATOR ''),
 ' FROM dm_generics ', GROUP_CONCAT(CONCAT('
     LEFT JOIN dm_generics   AS t_', REPLACE(field_name, '', ''), '
            ON dm_generics.dm_id = t_', REPLACE(field_name, '', ''), '.dm_id
           AND t_', REPLACE(field_name, '', ''), '.field_name = ', QUOTE(field_name)
   ) SEPARATOR ''),
 ' GROUP BY dm_generics.dm_id'
) INTO @qry FROM (SELECT DISTINCT field_name FROM dm_generics) t;";
$sql2   = "PREPARE stmt FROM @qry;";
$sql3   = "EXECUTE stmt;";

$stmt   = $dbh->prepare($sql);
$stmt2  = $dbh->prepare($sql2);
$stmt3  = $dbh->prepare($sql3);

if($stmt->execute() && $stmt2->execute() && $stmt3->execute())
{
     return $stmt3->fetchAll(PDO::FETCH_OBJ);
}

PDO准备语句中的Mysql变量

0 个答案: