php - 带有 COUNT 别名的 MySQL UNION

Question

我试图从两个单独的表中检索两个计数到一个 SQL 查询中以与 PHP 一起使用。这是当前的 SQl 查询:

SELECT COUNT(entryid) AS total FROM rh_entries UNION SELECT COUNT(pentryid) AS attended FROM rh_playerentries WHERE playerid=79

这是我用来利用数据的 PHP: $result = mysql_query($query);

$attendance = mysql_fetch_assoc($result);
echo "Total: " . $attendance['total'] 
 . " Attended: " . $attendance['attended'] 
 . " Percentage: " 
 . (int)$attendance['total'] / (int)$attendance['attended'] 
 . " <br />";

我得到这个输出:

Warning: Division by zero in /home/content/g/V/i/gViscardi/html/guilds/sanctum/raidinfo/player.php on line 41
Total: 6 Attended: Percentage: 

显然 $attendance['attended'] 设置不正确。我是否缺少有关 UNION、COUNT 或 AS 工作原理的信息？

Answer 1

联合将两个查询的内容合并到一个表中。您的查询具有不同的列名，因此合并将无法正常进行。你会想要这样的东西:

SELECT 
    (SELECT COUNT(entryid) FROM rh_entries) as total, 
    (SELECT COUNT(pentryid) FROM rh_playerentries WHERE playerid=79) as attended;