Oracle SQL相關子查詢：不是單組功能

Question

我正試圖計算出去醫生的旅行，並總結了多少費用。我正在使用ORACLE XE 11g和SQL Developer。我想這樣做與在選擇相關子查詢，但我得到這個消息：

ORA-00937: not a single-group group function 
00937. 00000 - "not a single-group group function" 
*Cause:  
*Action: 
Error at Line: 2 Column: 11 

這是我的查詢談到：

SELECT person.name, person.surname, COUNT(DISTINCT travelID) AS numberoftravels, 
    (SELECT SUM(costs.cost) FROM costs 
    JOIN travel ON costs.travelID = travel.travelID 
    JOIN person ON travel.personID = person.personID 
    JOIN staff ON travel.personID = staff.staffID 
    WHERE stafftype = 'Doctor' AND costtype = 'tolls' and staff1.staffID = person.personID 
) AS tollscost 

FROM travel JOIN person ON person.personID = travel.personID 
    JOIN staff staff1 ON staff1.staffID = person.personID 

WHERE stafftype = 'Doctor' 
GROUP BY person.name, person.surname; 

計數工作就好了之前我說子查詢。有誰知道我爲什麼會遇到這個問題？

Answer 1

您錯過了GROUP BY列 - personID