使用带有两个查询的php if…else语句

我有两个查询，用于计算数据库中“艺术家”和“组”的数据数量。如果有艺术家或组（或两者）的数据要显示，我想显示一条消息，如果两个艺术家或组（或两者）的数据都返回0，则不显示任何内容

我有以下代码似乎不起作用：

<?php if (($numrowsartists==0)OR($numrowsgroups==0)) {

 } else {
        echo "There is information to display.";
        }
?>

---

提前谢谢。我相信这可能是一个超级基本的修复程序，但我对php还是很陌生，希望能得到一些帮助。

您应该从行中获取值，例如使用别名作为列名

$query = "SELECT COUNT(*) as num_artists  FROM `Credit_To_Artist` AS c2a 
INNER JOIN `Credits` AS cr ON cr.credit_id = c2a.credit_id
INNER JOIN `Artist` AS a ON a.artist_id = c2a.artist_id
WHERE c2a.song_id = $id";

$res = mysql_query($query);

$row = mysql_fetch_assoc($res);
$numrowsartists = row['num_artists'];

$query = "SELECT COUNT(*) as  num_groups FROM `Credit_To_Artist` AS c2a 
INNER JOIN `Credits` AS cr ON cr.credit_id = c2a.credit_id
INNER JOIN `Artist_Group` AS ag ON ag.group_id = c2a.group_id
WHERE c2a.song_id = $id
ORDER BY ag.group_name ASC";

$res = mysql_query($query);
$row = mysql_fetch_assoc($res);
$numrowsgroups = row['num_groups'];

---

有几种解决方案，最简单的是：

if($numrowsartists[0]+$numrowsgroups[0] > 0)

然而，正如人们所说，您不应该再使用mysql_*函数了。 假设ID是用户输入，您应该真正使用准备好的语句。 此外，您可以在一个查询中处理这两个测试：

$stmt = $con->mysqli_prepare("SELECT COUNT(1) as `count` FROM `Credit_To_Artist` AS c2a 
      INNER JOIN `Credits` AS cr ON cr.credit_id = c2a.credit_id
      INNER JOIN `Artist` AS a ON a.artist_id = c2a.artist_id
      INNER JOIN `Artist_Group` AS ag ON ag.group_id = c2a.group_id
      WHERE c2a.song_id = ?");
$stmt->bind_param('i',$id);
$stmt->execute();
if($stmt->get_result()->fetch_array()[0] > 0){
    ...
}else{
    //message that nothing was found
}

---

mysql_*函数在PHP5.5.0中被弃用，在PHP7.0.0中被删除。将代码切换为使用或替代。

mysql\u fetch\u assoc

获取一行，因此它不等于0。使用num_rows函数来计算行数。您应该发布数据库架构和值。您还需要记住

NULL

！=<代码>0或“空”。

$stmt = $con->mysqli_prepare("SELECT COUNT(1) as `count` FROM `Credit_To_Artist` AS c2a 
      INNER JOIN `Credits` AS cr ON cr.credit_id = c2a.credit_id
      INNER JOIN `Artist` AS a ON a.artist_id = c2a.artist_id
      INNER JOIN `Artist_Group` AS ag ON ag.group_id = c2a.group_id
      WHERE c2a.song_id = ?");
$stmt->bind_param('i',$id);
$stmt->execute();
if($stmt->get_result()->fetch_array()[0] > 0){
    ...
}else{
    //message that nothing was found
}