根据用户排名而不是得分排名

Question

我有一个问题，我无法包裹我的头。

我正在使用Laravel框架。

我试图让基于位置排序表（即用户没有任何得分，他们只是有个展示位置）

我它是如何想的工作方式如下：

用户A =放置：1个

用户B =放置：10

用户B战胜用户A，然后用户B被放置为数1和用户A被放置为数2，然后我希望它相应地更新所有其他用户。

我似乎无法找到一个可靠的方法来做到这一点。

Answer 1

我不认为这是一个Laravel挑战，而是一个SQL挑战。解决这个问题可能很简单：基本上，你会询问失败者的实际位置，如果位置大于赢家，你什么都不做，否则你将把失败者的位置分配给新的赢家并更新表格的其余部分在位置列中加+1。

在代码中它会是这样的：

$winner_player = User::where('id', userA->id)->first(); 
$loser_player = User::where('id', userB->id)->first(); 

if($winner_player->position < $loser_player->position) { 
    //Update the rest of the users. 
    //We add 2 because we need space for the new winner and for 
    //the loser that is still above of the rest of the players. 
    DB::table('users') 
     ->where('position', '>', $loser_player->position) 
     ->update(DB::raw('position+2')); 

    //Set the winner with the actual position of the loser. 
    $winner_player->position = $loser_player->position; 
    $winner_player->save(); 

    //Set the looser with the new position (+1 of his actual). 
    $loser_player->position = $loser_player->position + 1; 
    $loser_player->save(); 
} 

修订LOGIC 作为分类中指出，它绕着行，但不这样做是正确，所以我更新逻辑使其按照预期工作，而且会稍微简单一些。

$winner_player = User::where('id', userA->id)->first(); 
$loser_player = User::where('id', userB->id)->first(); 

if($winner_player->position < $loser_player->position) { 
    //Set the winner with the actual position of the loser. 
    $winner_player->position = $loser_player->position; 

    //Update the users between the swap. There is no need to update 
    //the whole table, we only update the records between the swap. 
    DB::table('users') 
     ->where([['position', '<', $winner_player->position], 
       ['position', '>=', $loser_player->position]]) 
     ->update(DB::raw('position+1')); 

    //Save the value of the winner AFTER updating the positions 
    //between winner and loser. 
    $winner_player->save(); 
}