Question

<?php
include 'db.php';
$i=0;
$result15=mysql_query("select c.dishes from c");
 while($row=mysql_fetch_array($result15))
{
  if($row['dishes']!=NULL)
  {
  $dish[$i]=$row['dishes'];
 $i++;
}

}

  //$j=0;
 //while($j<$i)
 $j=0;
 while($j<$i)
 {

$result16=mysql_query("select * from dish_box where dish_name='$dish[$j]'");
while($row=mysql_fetch_array($result16))
{
    $v_id=$row['dish_id'];
    echo $v_id.'<br />';
}
$j++;

 }

 mysql_close();
 ?>

此while循环仅回显一次值。请弄清楚为什么循环工作一次？

Answer 1

或许更好的解决方案：

// if you're using user input here, be sure to use mysql_real_escape_string
/*
  $dishes = "'";
  foreach( $dish as $key => $val ) 
       $dishes .= "'" . mysql_real_escape_string( $val ) . "',";
  $dishes = substr( $dishes, 0, strlen( $dishes ) -2 ); // remove last ,
*/
// otherwise implode the list
$dishes = "'".implode("','", $dish)."'";

// in either case use the IN operator
// the semi-colon that was in the query won't work.
$result16=mysql_query("select * from dish_box where dish_name in ($dishes)");
// to confirm how many rows
echo "result16 returned " . mysql_num_rows($result16) . 'rows.';
while($row=mysql_fetch_array($result16))
{
    $v_id=$row['dish_id'];
    echo $v_id.'<br />';
}

我刚刚回忆起你在another question做了类似的事情。实际上，您可以将两个查询组合在一起并节省一些时间：

$result16=mysql_query("select * from dish_box where dish_name in ".
                      "(select c.dishes from c)");
while($row=mysql_fetch_array($result16))
{
    $v_id=$row['dish_id'];
    echo $v_id.'<br />';
}

Answer 2

您在$result16中存储的查询很可能只返回一行。尝试做：

$result16 = mysql_query(...);
echo "Total rows: ", mysql_num_rows($result16), "<br />";
while (...) {
etc.....

同样，您可能想尝试：

$result16 = mysql_query(...) or die(mysql_error());

假设您的查询成功，只会在事情失败时引起痛苦。

Answer 3

     $i=5;   
$j=0;
while($j<$i)
{

$result16=mysql_query("select * from dish_box where dish_name='$dish[$j]'");
while($row=mysql_fetch_array($result16))
{

$v_id[]=$row['dish_id'];
}
$j++;

}
var_dump($v_id);

你用每个循环覆盖$ v_id的值 - 因此它只会返回最后一个值。使$ v_id成为一个数组并写入它将有助于

PHP / MYSQL while循环问题

3 个答案: