Question

我想知道我是否可以在这个SQL查询上获得一些帮助。这是我失败后现在想要学习的测试。我花了很多时间在它上面，看了sql上的教程，但我仍然不知道如何编写它...

有2个表（航班，Occup_flights），包含航班信息，任务是：写一个查询，列出接下来7天的航班列表，并显示航班，可用座位数，占用数量座位和占用座位的百分比。

FLIGHTS:                    
FLIGHT  ID_COMPANY   DATE      ORIGIN   DESTINATION PLACES
1003       D3      20/01/2006   MADRID  LONDRES       40
1007       AF      20/01/2006   PARIS   MALAGA        12
1003       15      30/01/2006   MADRID  LONDRES       20
1007       AF      30/01/2006   PARIS   MALAGA        17

（地点显示每个航班提供的地点数量）

OCCUPATION_FLIGHTS:
FLIGHT ID_COMPANY   DATE    PASSENGER   SEAT
1003    IB       20/01/2006 07345128H   01V
1003    IB       20/01/2006 1013456213  01P
1003    IB       20/01/2006 08124356C   02V
1003    IB       20/01/2006 57176355K   02P
1007    AF       20/01/2006 27365138A   
1003    IB       30/01/2006 734512811   01V
1003    IB       30/01/2006 1013456213  02V
1003    IB       30/01/2006 57176355K

（当SEAT为空时，表示某人尚未签发机票）。 TEST DATA 我想要获得一些可用的座位我应该总结每个航班和日期乘客不是空的情况并从地方提取。所以我开始喜欢smth：

SELECT 
f.flight, 
f.places - (SELECT (CASE WHEN of.passanger IS NOT NULL THEN 1 ELSE 0 END)      
FROM occupation_flights AS of GROUP BY of.flight, of.date) AS available,
f.places - (SELECT (CASE WHEN of.passanger IS NULL THEN 1 ELSE 0 END) FROM occupation_flights AS of GROUP BY of.flight, of.date) AS occupied,
100.0 * ((f.places - (SELECT (CASE WHEN of.passanger IS NOT NULL THEN 1 ELSE 0 END) FROM occupation_flights AS of GROUP BY of.flight, of.date)) / f.places AS %occupied
FROM flights AS f
JOIN occupation_flights AS of ON f.flight=of.flight
WHERE f.date BETWEEN DateAdd(DD,-7,GETDATE() ) and GETDATE() 
GROUP BY f.flight

但它没有完成，因为我真的不明白如何让他同时按航班和日期分组计算，因为有相同航班号但是在不同日期的航班。我也无法访问表，测试是在纸上，并表明你知道如何编写SQL查询。对任何见解都会非常感激！非常感谢提前！

Answer 1

Mysql符合： SQLFIDDLE

SELECT f.flight,f.mydate,f.places - count(of.seat) as available_seats,
        count(of.seat) as occupied,
        count(of.seat)/f.places * 100 as percentage_occupied
FROM flights f
JOIN occupation_flights of
ON f.flight = of.flight AND f.mydate = of.mydate
WHERE of.mydate BETWEEN DATE_ADD(CURDATE(), INTERVAL -7 DAY)AND CURDATE() 
group by f.flight, f.mydate

Answer 2

select t1.flight,
   t1.date,
   t1.places,
   t3.c,
   t1.places-IFNULL(t3.c, 0) as empty
from flights t1 
left join(
    select count(t2.seat) as c, t2.flight, t2.date
        from occupation_flights t2
    where seat is not null
        group by flight, date
        ) t3 
    on t1.flight= t3.flight and t1.date= t3.date

，这是结果

enter image description here

PS。在我的代码中，使用了一个MySql函数IFNULL（），它应该被另一个数据库工具中的其他类似函数替换。

Answer 3

SELECT
    f.flight, f.mydate, f.id_company, origin, destination,
    places, (places - COALESCE(t.ocupped_seats, 0)) as available_places,
    IFNULL(t.ocupped_seats, 0) as ocupped_places,
    CONCAT(ROUND(COALESCE(places/COALESCE(t.ocupped_seats, 0), 0), 2), '%') as percentage
FROM
    flights as f
LEFT JOIN
    (SELECT
         flight, mydate,id_company, COUNT(seat) as ocupped_seats
     FROM
         occupation_flights
     WHERE
         seat IS NOT NULL
     GROUP BY
         flight, mydate) as t
     ON
         f.flight = t.flight AND f.mydate LIKE t.mydate
WHERE
    f.mydate BETWEEN CURDATE() AND CURDATE()+7

DEMO（感谢Jeremy C.用于构建架构，Strawberry用于COALLESCE函数）

结果：

enter image description here

如何编写此SQL查询？

3 个答案: