伯爵在Oracle

Question

我寫了下面的查詢嘗試數着去一個特定城市的航班數量，但我不能讓它工作

SELECT F.FLI_ID, A.AIRPORT_ID, C.CITY_ID 
FROM FLIGHT F INNER JOIN (AIRPORT A INNER JOIN CITY C ON A.CITY_ID = C.CITY_ID) 
ON F.ARRV_AIRPORT = A.AIRPORT_ID 
WHERE C.CITY_ID = 1000 
GROUP BY F.FLI_ID, A.AIRPORT_ID, C.CITY_ID; 

息率

FLI_ID AIRPORT_ID CITY_ID 
---------- ---------- ---------- 
     19   1  1000 
     11   1  1000 

應收益

NO.FLIGHTS AIRPORT_ID CITY_ID 
---------- ---------- ---------- 
     2   1  1000 

我曾嘗試下面的查詢

SELECT COUNT(F.FLI_ID) AS NO_FLIGHTS, A.AIRPORT_ID, C.CITY_ID 
FROM FLIGHT F INNER JOIN (AIRPORT A INNER JOIN CITY C ON A.CITY_ID = C.CITY_ID) 
ON F.ARRV_AIRPORT = A.AIRPORT_ID 
WHERE C.CITY_ID = 1000 
GROUP BY F.FLI_ID, A.AIRPORT_ID, C.CITY_ID; 

，我得到以下結果

NO_FLIGHTS AIRPORT_ID CITY_ID

---

 1   1  1000 
    1   1  1000 

Answer 1

你不應該按相同的值，你'正在努力計數......這就是爲什麼最終每行都會有一個計數。

更改GROUP BY來自：

GROUP BY F.FLI_ID, A.AIRPORT_ID, C.CITY_ID; 

要：

GROUP BY A.AIRPORT_ID, C.CITY_ID; 

它給你以下查詢：

SELECT COUNT(F.FLI_ID) AS NO_FLIGHTS, A.AIRPORT_ID, C.CITY_ID 
FROM FLIGHT F INNER JOIN (AIRPORT A INNER JOIN CITY C ON A.CITY_ID = C.CITY_ID) 
ON F.ARRV_AIRPORT = A.AIRPORT_ID 
WHERE C.CITY_ID = 1000 
GROUP BY A.AIRPORT_ID, C.CITY_ID; 

Answer 2

嘗試

SELECT count(1) as NUM_FLIGHTS, A.AIRPORT_ID, C.CITY_ID 
FROM FLIGHT F INNER JOIN (AIRPORT A INNER JOIN CITY C ON A.CITY_ID = C.CITY_ID) 
ON F.ARRV_AIRPORT = A.AIRPORT_ID 
WHERE C.CITY_ID = 1000 
GROUP BY A.AIRPORT_ID, C.CITY_ID; 

Answer 3

從GROUP BY中刪除FLI_ID。通過將其放入，您需要強制統計總計每FLI_ID的航班數量，該數量始終爲1，因此您將爲每個航班ID獲取一行。

SELECT COUNT(F.FLI_ID) AS NO_FLIGHTS, A.AIRPORT_ID, C.CITY_ID 
FROM FLIGHT F INNER JOIN (AIRPORT A INNER JOIN CITY C ON A.CITY_ID = C.CITY_ID) 
ON F.ARRV_AIRPORT = A.AIRPORT_ID 
WHERE C.CITY_ID = 1000 
GROUP BY A.AIRPORT_ID, C.CITY_ID;