MySQL用if语句选择COUNT（*）

Question

我有1个表有很多记录，我想分开COUNT(*)值（盈利/亏损），我可以用2个MySQL查询来做，但我想用1个查询来做那可能吗？

$query_string = '
        SELECT 
            MONTH(order_time) AS month,
            CASE WHEN order_profit > 0 THEN COUNT(*) END AS profit,
            CASE WHEN order_profit < 0 THEN COUNT(*) END AS loss,
            COUNT(*) AS total
        FROM
            trade_histories
    ';
$query_string .= '
        WHERE
            order_profit IS NOT NULL
    ';
$query_string .= '
        GROUP BY
            MONTH(order_time) 
    ';

这是我到目前为止所尝试的，这就是结果

stdClass Object ( [month] => 1 [profit] => 447 [loss] => [total] => 447 ) 
stdClass Object ( [month] => 2 [profit] => 1153 [loss] => [total] => 1153 ) 
stdClass Object ( [month] => 3 [profit] => 898 [loss] => [total] => 898 ) 
stdClass Object ( [month] => 4 [profit] => [loss] => 640 [total] => 640 ) 
stdClass Object ( [month] => 12 [profit] => [loss] => 2 [total] => 2 )