Question

如何检查mysql结果是否为空。如果mysql查询结果为空，则不应该删除condtion。如果mysql结果数据那里＆amp; in else条件我的错误我的消息在那里，但它没有显示任何错误消息。我尝试了以下代码，但没有在屏幕上显示任何警报或回显消息。

＆＃13;

<?php
$sql = "select * from hall_search_data_1 where rent BETWEEN '".$_SESSION['amount1']."' AND '".$_SESSION['amount2']."'";
$res = mysql_query($sql);
if(!empty($res)){
while($row=mysql_fetch_row($res))
{
// here my data 
}
}else{
echo "no results found";
echo "<br>";
echo "<script>alert('No any result found..!!');</script>";
echo "no results found";
}
?>

＆＃13;

Answer 1

＆＃13;

    <?php
    $servername = "localhost";
    $username = "username";
    $password = "password";
    $dbname = "myDB";
    $conn = new mysqli($servername, $username, $password, $dbname);
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }
    $sql = "SELECT id, firstname, lastname FROM MyGuests";
    $result = $conn->query($sql);
    if ($result->num_rows > 0) {
        while ($row = $result->fetch_assoc()) {
            echo "id: " . $row["id"] . " - Name: " . $row["firstname"] . " " . $row["lastname"] . "<br>";
        }
    } else {
        echo "0 results";
    }
    $conn->close();
    ?>

＆＃13;

Answer 2

检查行数

$result = mysqli_query($conn, $sql);
$rowcount=mysqli_num_rows($result); 
if($rowcount > 0){ 
  echo "Number of rows = " . $rowcount;
  }
  else
  { 
  echo "no record found"; 
  }

Answer 3

安全提示：首先停止使用mysql_*函数，因为它们对生产不安全，并且更高版本已停止对此API的支持。因此，如果不小心在生产中使用了这些功能，则可能会遇到麻烦。

不建议将旧的mysql扩展用于新开发，因为它在PHP 5.5.0中已弃用，在PHP 7中已删除。下面提供了详细的功能比较矩阵。 More Read

对于您的答案，您只需检查no of rows是否为零通过示例阅读php documentation处的帖子。

mysqli_num_rows

Answer 4

您可以使用mysql_num_rows检查结果集的编号：

    $sql = "select * from hall_search_data_1 where rent BETWEEN '".$_SESSION['amount1']."' AND '".$_SESSION['amount2']."'";
    $res = mysql_query($sql);
if(isset($res))
{
$noRows = mysql_num_rows($res);
    if($noRows > 0){
    while($row=mysql_fetch_row($res))
    {
    here my data 
    }
    }else{
    echo "no results found";
    echo "<br>";
    echo "<script>alert('No any result found..!!');</script>";
    echo "no results found";
    }
}

在这里找到mysql_num_rows的文档：

mysql_num_rows

Answer 5

您可以使用mysql_num_rows();检查查询返回行是否

$sql = "select * from hall_search_data_1 where rent BETWEEN '".$_SESSION['amount1']."' AND '".$_SESSION['amount2']."'";
$res = mysql_query($sql);
$rows=mysql_num_rows($res);
if($rows>0)
{
   echo "data return from query";
}else{

echo "data not return";
}

注意： - 不推荐使用mysql而是使用mysqli或PDO

Answer 6

您可以使用mysql_num_rows来获取查询返回的行数。

if(mysqli_num_rows($res) > 0)
{
    // rest of your stuff
}
else
{
    echo "No records found.";
}

注意：不推荐使用mysql而是使用mysqli或PDO，如上所示

Answer 7

你可以用这样的mysql_num_rows替换if(!empty($res)) -

$sql = "select * from hall_search_data_1 where rent BETWEEN '".$_SESSION['amount1']."' AND '".$_SESSION['amount2']."'";
$res = mysql_query($sql);
if($countrows = mysql_num_rows($res) >= 1){
    while($row=mysql_fetch_row($res))
    {
        here my data 
    }
}else{
    echo "no results found";
    echo "<br>";
    echo "<script>alert('No any result found..!!');</script>";
    echo "no results found";
}

Answer 8

mysql_* API早已从PHP中删除。要访问数据库，您应该使用PDO。检查PDO是否返回任何结果实际上非常简单。 仅获取结果，如果数组为空，则MySQL没有任何返回。

$stmt = $pdo->prepare('SELECT * FROM hall_search_data_1 WHERE rent BETWEEN ? AND ?');
$stmt->execute([$_SESSION['amount1'], $_SESSION['amount2']]);
$records = $stmt->fetchAll();
if ($records) {
    foreach ($records as $row) {
        // your logic
    }
} else {
    echo 'No records found!';
}

还有mysqli库，如果您坚持使用它，则必须做更多的工作，但是想法是相同的。获取所有结果，如果没有获取任何内容，则意味着MySQL不返回任何行。

$stmt = $mysqli->prepare('SELECT * FROM hall_search_data_1 WHERE rent BETWEEN ? AND ?');
$stmt->bind_param('ss', $_SESSION['amount1'], $_SESSION['amount2']);
$stmt->execute();
$records = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);
if ($records) {
    foreach ($records as $row) {
        // your logic
    }
} else {
    echo 'No records found!';
}

如何在PHP中检查MySQL结果是否返回空？

8 个答案: