Question

在下表中，我试图找到以下声明：对于每个员工，显示每个员工的监督人数？

NAME                SSN       BDATE     SEX     SALARY SUPERSSN  DNO
------------------- --------- --------- --- ---------- --------- --------
John B Smith        123456789 09-JAN-55 M        30000 333445555 5
Franklin T Wong     333445555 08-DEC-45 M        40000 888665555 5
Alicia J Zelaya     999887777 19-JUL-85 F        25000 987654321 4
Jennifer S Wallace  987654321 20-JUN-31 F        43000 888665555 4
Ramesh K Narayan    666884444 15-SEP-52 M        38000 333445555 5
Joyce A English     453453453 31-JUL-62 F        25000 333445555 5
Ahmad V Jabbar      987987987 29-MAR-59 M        25000 987654321 4
James E Borg        888665555 10-NOV-27 M        55000

我可以找到员工和主管，但不知道如何计算：

SQL> select e.name, s.name, count(*) from jps.employee e, jps.employee s where e.superssn = s.ssn group by e.name, s.name; 

NAME                NAME                  COUNT(*)
------------------- ------------------- ----------
Ahmad V Jabbar      Jennifer S Wallace           1
Joyce A English     Franklin T Wong              1
Alicia J Zelaya     Jennifer S Wallace           1
Jennifer S Wallace  James E Borg                 1
Franklin T Wong     James E Borg                 1
John B Smith        Franklin T Wong              1
Ramesh K Narayan    Franklin T Wong              1

从上面的结果中，您可以看到富兰克林有3名他监督的员工。我怎么算他们？

提前谢谢你，尼尔斯。

Answer 1

您可以使用＆＃34; GROUP BY＆＃34;函数使用Name列（在您的情况下是e.name或s.name）。

有关详细信息，请参阅此link

Answer 2

我找到了这个例子：Counting child for parent我觉得这就是解决方案：

SQL> select s.name, count(e.name) from jps.employee e, jps.employee s where e.superssn = s.ssn group by s.name;

Answer 3

SELECT COUNT(E.NAME) AS ENAME,  S.NAME
FROM JPS.EMPLOYEE E INNER JOIN JPS. EMPLOYEE S 
ON E.SUPERSSN = S.SSN
GROUP BY  S.NAME

员工数量有困难

3 个答案: