如何用条件计算多行

Question

因此，我试图让查询计算该位置的玩家总数，如果他们在相同的位置和在线。但我目前的查询返回0.不知道要尝试什么，一直卡住了几天。

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Answer 1

这是你的问题：

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

你必须在引号代替反引号 “在线”。

Answer 2

请记住，PHP的mysql_ *函数正在死亡，切换到mysqli或pdo之类的东西或其他东西。在我提交的代码中查看我的评论。 告诉我，如果它的工作。干杯。

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'];