mysql - 如何编写此 SQL 查询？

Question

我想知道是否可以就此 sql 查询获得一些帮助。它来 self 失败的测试，现在想学习。我在上面花了很多时间，看了有关 sql 的教程，但我仍然不明白它是如何编写的。

有 2 个表(flights，occupation_flights)包含航类信息，任务是:编写一个查询，给出接下来 7 天的航类列表，并显示航类、可用座位数、占用人数席位和已占用席位的百分比。

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

(PLACES 显示每个航类提供的座位数)

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，表示还没有人出票)。 TEST DATA 我想获得一些可用座位，我应该总结每个航类和日期乘客不空的情况，并从 PLACES 中提取。 所以我从以下开始:

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

但是还没完，因为我实在不明白怎么让他同时按航类和日期分组计算，因为有航类号相同但去的日期不同的航类。我也无权访问表，测试是在纸上进行的，以表明您知道如何编写 sql 查询。 真的很感激任何见解! 非常感谢!

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