Question

$allUsersResult = mysql_query("SELECT * FROM users");

// the purpose of this line was to grab the first row for use 
// separately in a different area than the while loop
$user = mysql_fetch_assoc($allUsersResult);


while($users = mysql_fetch_assoc($allUsersResult)){

 // the first row is not available here

}

这是一个错误还是我做错了我的错？

PS：这只是举例。我没有像这样使用$ user和while循环，它们在脚本的不同位置使用。

Answer 1

你需要放弃

$allUsers = mysql_fetch_assoc($allUsersResult);

这是你的第一个结果行。

回答新问题：不。这不是PHP的设计缺陷。这是程序设计中的一个缺陷。你需要重新思考你在做什么。

为什么需要分离出第一个值？您是否一直依赖它来自您的桌子中的特定行？如果您更改了表格架构，那么非常可能将使用其他排序顺序将结果返回给您。

也许如果你告诉我们你想做什么，我们可以给你一些设计建议。

Answer 2

这是你的错。首先调用$allUsers = mysql_fetch_assoc($allUsersResult);，您已经从结果集中获取第一行。所以只需删除该行，它应该按预期工作。

编辑：评论中的每个请求。

$user = mysql_fetch_assoc($allUsersResult);
if ( $user ) // check if we actually have a result
{
    // do something special with first $user

    do
    {
        // do the general stuff with user
    }
    while( $user = mysql_fetch_assoc($allUsersResult) );
}

Answer 3

某些IDE认为这是错误的代码（一行中有两个语句）。更好：

$allUsersResult = mysql_query("SELECT * FROM users");
$user = mysql_fetch_assoc($allUsersResult);

while($user){

    // do stuff
    doStuff($user)

    // at last: get next result
    $user = mysql_fetch_assoc($allUsersResult)


}

Answer 4

使用mysql_fetch_assoc()时，基本上是检索行，然后推进内部结果指针+1。

为了更好地解释，这是您的代码：

$allUsersResult = mysql_query("SELECT * FROM users");
//Result is into $allUsersResult... Pointer at 0


$user = mysql_fetch_assoc($allUsersResult);
// $user now holds first row (0), advancing pointer to 1 


// Here, it will fetch second row as pointer is at 1...
while($users = mysql_fetch_assoc($allUsersResult)){

 // the first row is not available here

}

如果您想再次获取第一行，不需要再次运行查询，只需在读完第一行后将指针重置为0 ...

$allUsersResult = mysql_query("SELECT * FROM users");
//Result is into $allUsersResult... Pointer at 0


$user = mysql_fetch_assoc($allUsersResult);
// $user now holds first row (0), advancing pointer to 1 

// Resetting pointer to 0
mysql_data_seek($allUsersResult, 0);

// Here, it will fetch all rows starting with the first one
while($users = mysql_fetch_assoc($allUsersResult)){
  // And the first row IS available
}

PHP Documentation: mysql_data_seek()

Answer 5

我会继续回答我自己的问题：

    $allUsersResult = mysql_query("SELECT * FROM users");

    // transfer all rows to your own array immediately
    while($user = mysql_fetch_assoc($allUsersResult)){
       $allUsers[] = $user;
     }

    // use first row however you like anywhere in your code
    $firstRow = $allUsers[0];

    // use all rows however you like anywhere in your code
    foreach($allUsers as $user){
      // do whatever with each row ($user). Hey look they're all here! :)
    }

这是PHP还是MySQL的错误？

5 个答案: