Question

我已经注释掉了底部，SQL查询工作正常。它显示错误来自我相信的查询。

$host = "127.0.0.1"; 
$user = "root"; 
$pass = "Toom13371!";

$connection = mysql_connect($host,$user,$pass) or die (mysql_errno().":     ".mysql_error()."<BR>");

// 2. Selecting DB.

$dbname = "filters"; 
mysql_select_db($dbname);

// 3. Build/Test SQL Query

$sql = ("select * from filter_bandpass where start_passband=" . $_POST['Lowfreq'] . "         and stop_passband='" . $_POST['Highfreq'] . "'");
//echo $sql; //Comment/Uncomment to test sql query.

// 4. Retrieve info from MySQL.

$query = mysql_query($sql);

// 5. Display Query.

echo "<table border='1'>
<tr>
<th>Low Frequency</th>
<th>High Frequency</th>
</tr>";

while($row = mysql_fetch_array($query)) {
  echo "<tr>";
  echo "<td>" . $row['Lowfreq'] . "</td>";
  echo "<td>" . $row['Highfreq'] . "</td>";
  echo "</tr>";
}

echo "</table>";
  ?>

任何帮助都会受到赞赏，我确定它会成为一个小小的愚蠢错误。

提前致谢：）

Answer 1

我根据您的查询猜测您需要更改此

mysql_select_db($dbname);

到

mysql_select_db($dbname, $connection);

和

while($row = mysql_fetch_array($query)) {
  echo "<tr>";
  echo "<td>" . $row['Lowfreq'] . "</td>";
  echo "<td>" . $row['Highfreq'] . "</td>";
  echo "</tr>";
}

到

while($row = mysql_fetch_array($query)) {
  echo "<tr>";
  echo "<td>" . $row['start_passband'] . "</td>";
  echo "<td>" . $row['stop_passband'] . "</td>";
  echo "</tr>";
}

Answer 2

更改行

mysql_select_db($dbname);

到

mysql_select_db($dbname, $connection);

在查询之前

$_POST['Lowfreq']和$_POST['Highfreq']

如果这些变量中没有值，则查询必须返回空。

Answer 3

在您的查询中，字符串不应包含括号。

 $sql = ("select * from filter_bandpass where start_passband=" . $_POST['Lowfreq'] . "         and stop_passband='" . $_POST['Highfreq'] . "'");

应该是：

 $sql = "select * from filter_bandpass where start_passband=" . $_POST['Lowfreq'] . "         and stop_passband='" . $_POST['Highfreq'] . "'";

PHP mysql查询返回一个空白屏幕

3 个答案: