php - php中num行的重复结果

Question

可能重复：
循环时我无法在里面创建 num 行

我尝试在循环中分配 num 行以获取另一个表的行数

$select_sub_cat = mysql_query("SELECT * FROM sub_cat WHERE ct_id='".$row_main['id']."' LIMIT 8 ");
while($row_sub = mysql_fetch_array($select_sub_cat))
{
  $select_num_sub = mysql_query("SELECT * FROM market WHERE sub_cat='".$row_sub['id']."'  ");
  while($row_num_sub = mysql_fetch_array($select_num_sub))
  {
    $n = mysql_num_rows($select_num_sub);
    $smarty->assign('n',$n);
  }

 $sub_cats[] = $row_sub;
}
$smarty->assign('sub_cats',$sub_cats);

Answer 1

mysql_num_rows 函数用于计算表中的行数，因此它将在 while 循环之前使用。

$select_sub_cat = mysql_query("SELECT * FROM sub_cat WHERE ct_id='".$row_main['id']."' LIMIT 8 ");
while($row_sub = mysql_fetch_array($select_sub_cat))
{
  $select_num_sub = mysql_query("SELECT * FROM market WHERE sub_cat='".$row_sub['id']."'  ");
  $n = mysql_num_rows($select_num_sub);
  while($row_num_sub = mysql_fetch_array($select_num_sub))
  {

    $smarty->assign('n',$n);
  }

 $sub_cats[] = $row_sub;
}
$smarty->assign('sub_cats',$sub_cats);

Answer 2

放置以下几行是没有意义的：

$n = mysql_num_rows($select_num_sub);
$smarty->assign('n',$n);

在内循环内部。如果要通过 smarty 显示查询的行数，只需：

$select_num_sub = mysql_query("SELECT * FROM market WHERE sub_cat='".$row_sub['id']."' 
$n = mysql_num_rows($select_num_sub);
$smarty->assign('n',$n);

在外循环里面，你会没事的。