通过单个查询获取多个表列的总和

Question

我有一个主表酒店及其子表hotel_food ， hotel_extras ， hotel_room和参考ID 酒店 ，

现在，我想获取每个酒店的每个表（hotel_food，hotel_extras，hotel_room）中的价格列总和。

现在我这样使用

$result = $db->query("SELECT id FROM hotel WHERE id = '.$hotel.'");
if($row = $result->fetch_array(MYSQLI_ASSOC)) {
   $food_result = $db->query("SELECT sum(price) FROM hotel_food WHERE hotel_id = '".$row['id']."'");
   $room_result = $db->query("SELECT sum(price) FROM hotel_room WHERE hotel_id = '".$row['id']."'");
   $extras_result = $db->query("SELECT sum(price) FROM hotel_extras WHERE hotel_id = '".$row['id']."'");
}

有没有办法通过单个查询获取所有表价格的总和，例如totalFoodPrice，totalRoomPrice，totalExtrasPrice

提前致谢

Answer 1

SELECT * FROM
(
 SELECT sum(price) AS totalFoodPrice FROM hotel_food WHERE hotel_id = 1,
 SELECT sum(price) AS totalRoomPrice FROM hotel_room WHERE hotel_id = 1,
 SELECT sum(price) AS totalExtrasPrice FROM hotel_extras WHERE hotel_id = 1
) temp

Answer 2

您可以使用如下子查询：

$result = $db->query("SELECT id, 
   (SELECT sum(price) FROM hotel_food WHERE hotel_id = h.id) TotalFoodPrice,
   (SELECT sum(price) FROM hotel_room WHERE hotel_id = h.id) TotalRoomPrice,
   (SELECT sum(price) FROM hotel_extras WHERE hotel_id = h.id) TotalExtraPrice
FROM hotel h WHERE id = '.$hotel.'");