Question

我想根据类型列出我数据库中的注释。

我的数据库中有三种类型的注释，我用三种不同的查询来调用它们。

//01 - Awaiting Comments
  $query = $handler->prepare("SELECT * FROM comments WHERE confirmed = 0");

  $query->execute();
  $r = $query->fetchAll(PDO::FETCH_ASSOC);
    echo "<h1>Awaiting Comments</h1>";
    foreach($r as $r_)  {
    echo "<li>r_[title]</li>";
  }
//02 - Comments waiting for confirmation
  $query = $handler->prepare("SELECT * FROM comments WHERE confirmed = 2");

  $query->execute();
  $r = $query->fetchAll(PDO::FETCH_ASSOC);
    echo "<h1>Comments waiting for confirmation</h1>";
    foreach($r as $r_)  {
    echo "<li>r_[title]</li>";
  }

//03 - Confirmed comments
  $query = $handler->prepare("SELECT * FROM comments WHERE confirmed = 1");

  $query->execute();
  $r = $query->fetchAll(PDO::FETCH_ASSOC);
    echo "<h1>Confirmed Comments</h1>";
    foreach($r as $r_)  {
    echo "<li>r_[title]</li>";
  }

使用我当前的代码，我得到了我想要的输出：

Awaiting Comments
-comment 1
-comment 8
-comment 5

Comments waiting confirmation
-comment 9
-comment 4
-comment 2

Confirmed Comments
-comment 3
-comment 6
-comment 7

有没有办法用单个查询而不是三个查询获得相同的输出？

Answer 1

PDO比每个人都认为的要多一点。例如，它有一个很棒的功能，称为PDO::FETCH_GROUP。

更不用说可以使您的代码显着缩短的其他一些小改进。

$r = $handler->query("SELECT confirmed, c.* FROM comments c")->fetchAll(PDO::FETCH_GROUP);

是您需要的所有代码。

在这里，您首先选择confirmed字段，然后告诉PDO根据其值对结果进行分组（或“乘法”）。

现在您可以随时随地打印您的评论

// Awaiting Comments
foreach($r[0] as $r_) {
    echo "<li>$r_[title]</li>";
}

// Confirmed comments
foreach($r[2] as $r_) {
    echo "<li>$r_[title]</li>";
}

或者，使其成为一个循环

$titles = [
    0 => 'Awaiting Comments',
    2 => 'Comments waiting confirmation',
    1 => 'Confirmed Comments',
];

foreach ($titles as $code => $title)
{
    echo "<h3>$title</h3>";
    foreach($r[$code] as $r_) {
        echo "<li>$r_[title]</li>";
    }
}

Answer 2

是的，您可以使用IN条件：

SELECT * FROM comments WHERE confirmed IN (0, 1, 2)

然后，您可以根据需要循环遍历结果以创建输出。

Answer 3

您可以使用此查询语法：

SELECT * FROM comments 
WHERE (confirmed >= 0 AND confirmed < 3 ) 
ORDER BY FIELD(confirmed,0,2,1)

通过这种方式，您可以按所需的输出排序所有行。

如果confirmed字段仅允许0,1,2值，您可以这样方式：

SELECT * FROM comments 
ORDER BY FIELD(confirmed,0,2,1)

然后：

while( $row = $query->fetch(PDO::FETCH_ASSOC) )
{
    if    ( $row['confirmed'] == 0 )
    {
        (...)
    }
    elseif( $row['confirmed'] == 1 )
    {
        (...)
    }
    else
    {
        (...)
    }
}

Answer 4

你可以这样做： SELECT * FROM comments WHERE confirmed=1 OR confirmed=2 OR confirmed=0 或者使用IN

如何多次查询结果以减少查询次数？

4 个答案: