oracle11g - ORA-00979: not a GROUP BY expression 错误，如何解决？

Question

SELECT ssn, fname, minit, lname, AVG(hours)
FROM EMPLOYEE, WORKS_ON
WHERE EMPLOYEE.ssn = WORKS_ON.essn
GROUP BY hours
ORDER BY AVG(hours) DESC

它显示 ORA-00979 错误：不是 GROUP BY 表达式

我想知道为什么它不起作用？顺便说一句，所有表都存在并且没有任何错误。它在 Oracle AE 11g ===========UPDATE========================== 请求的表

SSN FNAME   MINIT   LNAME   AVG(HOURS)
888665555   James   E   Borg    -
666884444   Ramesh  K   Narayan 40
999887777   Alicia  J   Zelaya  20
987987987   Ahmad   V   Jabbar  20
453453453   Joyce   A   English 20
123456789   John    B   Smith   20
987654321   Jennifer    S   Wallace 17.5
333445555   Franklin    T   Wong    7.33333333333333333333333333333333333333

Answer 1

我认为您的意思GROUP BY是聚合列：

SELECT ssn, fname, minit, lname, AVG(hours)
FROM EMPLOYEE, WORKS_ON
WHERE EMPLOYEE.ssn = WORKS_ON.essn
GROUP BY ssn, fname, minit, lname
ORDER BY AVG(hours) DESC

Answer 2

我认为你的分组与你需要的完全相反。你要：

SELECT ssn, fname, minit, lname, AVG(hours)
FROM EMPLOYEE, WORKS_ON
WHERE EMPLOYEE.ssn = WORKS_ON.essn
GROUP BY ssn, fname, minit, lname
ORDER BY AVG(hours) DESC

Answer 3

由于您使用的是聚合函数AVG(hours)，因此您需要对其余结果进行分组：

SELECT ssn, fname, minit, lname, AVG(hours)
FROM EMPLOYEE, WORKS_ON
WHERE EMPLOYEE.ssn = WORKS_ON.essn
GROUP BY ssn, fname, minit, lname
ORDER BY AVG(hours) DESC