伯爵在Oracle

Question

我写了下面的查询尝试数着去一个特定城市的航班数量，但我不能让它工作

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 

应收益

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

我曾尝试下面的查询

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; 

，我得到以下结果

NO_FLIGHTS AIRPORT_ID CITY_ID

---

 1   1  1000 
    1   1  1000 

Answer 1

你不应该按相同的值，你'正在努力计数......这就是为什么最终每行都会有一个计数。

更改GROUP BY来自：

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

要：

GROUP BY A.AIRPORT_ID, C.CITY_ID; 

它给你以下查询：

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

尝试

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

从GROUP BY中删除FLI_ID。通过将其放入，您需要强制统计总计每FLI_ID的航班数量，该数量始终为1，因此您将为每个航班ID获取一行。

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;