Question

我正在尝试执行此查询，但我收到错误“Undefined index： lname“。我想从表a和中计算一列（fname）中的行从其他表b中选择列（lname）。所以请帮助我。

    $result = mysql_query("SELECT COUNT(fname),lname FROM a,b");
    while ($row = mysql_fetch_array($result))
    {
      echo "<tr><td>";
      echo $row['lname'];
      echo "</td>";
      echo "<td>";
      echo $row['COUNT(fname)'];
      echo "</td></tr>";
    }

Answer 1

如果仍然出现错误，可以尝试单独获取两者：

$result = mysql_query("SELECT COUNT(fname) FROM a");
while ($row = mysql_fetch_array($result))
  {
    echo "<tr><td>";
    echo $row['COUNT(fname)'];
    echo "</td></tr>";

  }

$result1 = mysql_query("SELECT lname FROM b");
while ($row = mysql_fetch_array($result1))
    {
      echo "<tr><td>";
      echo $row['lname'];
      echo "</td></tr>";
   }

Answer 2

您需要使用别名。使用此：

$result = mysql_query("SELECT COUNT(fname) AS countfname,lname FROM a,b");
while ($row = mysql_fetch_array($result))
{
  echo "<tr><td>";
  echo $row['lname'];
  echo "</td>";
  echo "<td>";
  echo $row['countfname'];
  echo "</td></tr>";
}

Answer 3

试试这段代码：

$result = mysql_query("SELECT COUNT(a.fname) as fname,b.lname as lname FROM a,b");
while ($row = mysql_fetch_array($result))
{
  echo "<tr><td>";
  echo $row['lname'];
  echo "</td>";
  echo "<td>";
  echo $row['COUNT(fname)'];
  echo "</td></tr>";
}

如何从mysql中的两个表中选择两列

3 个答案: