Question

感谢您查看我的问题。我试图只更新我的数据库中的值，如果该字段为空（因此，如果有人试图注册一个已准备就绪的点并且将输出错误消息，则不会覆盖现有用户）。我已经列出了我尝试过的最新脚本中的2个。如果select语句不存在，则第一个脚本用于更新数据库，但如果在同一天和时间输入，则会覆盖用户。谢谢大家！

$sql = ("SELECT `player1` FROM `users` where id = '$id' and Times = '$time'"); 


$result = $conn->query($sql);

if ($result->fetch_assoc === NULL) {
$update_player = ("UPDATE users SET player1 = '$name' where id = '$id' AND Times =   '$time'")

if($update_player){
echo "Date for $name inserted successfully!";
}
}

else {
  echo 'That spot is all ready taken!';
}

//2nd script 

$query=mysql_query("UPDATE users SET 
player1 = isNULL (player1, $name) 
where id = '$id' AND Times = '$time'" );

if($query){

 echo "Data for $name inserted successfully!";
}

else {
 echo 'That spot is all ready taken!';
}

Answer 1

以下代码可以解决这个问题：

$query=mysql_query("UPDATE users SET 
player1='$name' 
where id = '$id' AND Times = '$time' AND player1 IS NULL" );

if(mysql_affected_rows() == 1){
  echo "Data for $name inserted successfully!";
}
else {
  echo 'That spot is all ready taken!';
}

请注意，您应该使用pdo或mysqli功能。

Answer 2

试试这个。

 while($row = $result->fetch_assoc) {
    if($row['player1'] == NULL){
      $update_player = ("UPDATE users SET player1 = '$name' where id = '$id' AND Times =   '$time'")
    }

仅在Null php / mysql时更新值

2 个答案: