如何用條件計算多行

Question

因此，我試圖讓查詢計算該位置的玩家總數，如果他們在相同的位置和在線。但我目前的查詢返回0.不知道要嘗試什麼，一直卡住了幾天。

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Answer 1

這是你的問題：

$totPlayers = mysql_query("SELECT COUNT(*) AS player_total FROM `user_info` WHERE `location` = '$town' AND `online` = '1'"); 

你必須在引號代替反引號 「在線」。

Answer 2

請記住，PHP的mysql_ *函數正在死亡，切換到mysqli或pdo之類的東西或其他東西。在我提交的代碼中查看我的評論。 告訴我，如果它的工作。乾杯。

include('connect.php'); 

$town = $info['location']; 

$grabTown = mysql_query("SELECT * FROM `location` WHERE `name` = '$town'"); 

// Added error check 
if (!$grabTown) { 
    die('Invalid query: ' . mysql_error()); 
} 

$t = mysql_fetch_array($grabTown); 

// Changed '' to `` on { 'online' } and removed '' from { '1' } 
// Don't know if removing '' on { '1' } is required. I think it's fine either way. 
$totPlayers = mysql_query("SELECT COUNT(*) AS player_total FROM `user_info` WHERE `location` = '$town' AND `online` = 1"); 

// Added error check 
if (!$totPlayers) { 
    die('Invalid query: ' . mysql_error()); 
} 

$totalPlayers = mysql_fetch_array($totPlayers); 
$playersTotal = $totalPlayers['player_total'];