根據用戶排名而不是得分排名

Question

我有一個問題，我無法包裹我的頭。

我正在使用Laravel框架。

我試圖讓基於位置排序表（即用戶沒有任何得分，他們只是有個展示位置）

我它是如何想的工作方式如下：

用戶A =放置：1個

用戶B =放置：10

用戶B戰勝用戶A，然後用戶B被放置爲數1和用戶A被放置爲數2，然後我希望它相應地更新所有其他用戶。

我似乎無法找到一個可靠的方法來做到這一點。

Answer 1

我不認爲這是一個Laravel挑戰，而是一個SQL挑戰。解決這個問題可能很簡單：基本上，你會詢問失敗者的實際位置，如果位置大於贏家，你什麼都不做，否則你將把失敗者的位置分配給新的贏家並更新表格的其餘部分在位置列中加+1。

在代碼中它會是這樣的：

$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(); 
} 

修訂LOGIC 作爲分類中指出，它繞着行，但不這樣做是正確，所以我更新邏輯使其按照預期工作，而且會稍微簡單一些。

$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(); 
}