mysql查询查询

Question

我知道这是一个愚蠢的问题，但是我是php的新手，所以任何帮助都是有用的。

我有两个表格， product和payment ：

• 产品表具有Id ， Room_Available ， price ，...
• 付款表具有Id ， Product_Id ， Total_Room ，...
• 产品表有很多记录

我期望的是，如果Occupied_Room <= Room_Available ，则条件为Status ='Y'，否则为Status ='N'，它将提供所有产品记录。

• cms_product.Room_Available是总房间可用
• cms_payment.Total_Room是已预订的房间

查询是：

SELECT SUM(cms_payment.Total_Room) as Occupied_Room,
    `cms_product`.`Room_Available` as Available_Room  
FROM 
(
    `cms_product` 
    LEFT JOIN `cms_payment` on (cms_product.`Id` = cms_payment.`Product_Id`)
)
GROUP BY `cms_product`.`Id` 
HAVING Occupied_Room <= Room_Available

Answer 1

在黑暗中有点刺伤，但是我想你想要：

SELECT Prod.Id, 
    CASE WHEN COALESCE(SUM(Pay.Total_Room),0) <= Prod.Room_Available THEN 'Y' 
         ELSE 'N'
    END AS Status
FROM cms_product AS Prod
LEFT JOIN cms_payment AS Pay ON Prod.Id = Pay.Product_Id
GROUP BY Prod.Id, Prod.Room_Available

这将显示所有产品ID和状态（ 'Y' =可用或已满； 'N' =超额预订）。

Answer 2

试试看：下表使用一些示例数据。 您可以将状态更改为y或n :)

SQLFIDDLE演示

select product.id, 
case when coalesce(x.sm,0) <= product.total_room then 
'available' else 'unavailable' end status,
product.total_room, coalesce(x.sm,0) as rooms_required
from product 
left join (
select payment.product_id, 
sum(payment.room_required) sm
from payment 
group by payment.product_id)x
on x.product_id = product.id
group by product.id
;


| ID |      STATUS | TOTAL_ROOM | ROOMS_REQUIRED |
--------------------------------------------------
|  1 | unavailable |         10 |             12 |
|  2 |   available |         15 |             15 |
|  3 |   available |          5 |              4 |
|  4 |   available |         10 |              0 |