SQL SELECT 查询从表中提取数据以计算总和

Question

我在数据库中有四个表，我想做的基本上是列出他们正在从事的任何项目的员工编号、部门编号以及他们在项目上花费的总小时数。

我试图将这一切作为一个单一的SELECT 语句来完成，但在让它与 Oracle SQL 一起工作时遇到了麻烦。我最近的尝试是

SELECT EMPLOYEE.E#, EMPLOYEE.NAME, SUM(WORKSON.HOURS)
FROM EMPLOYEE JOIN WORKSON ON EMPLOYEE.E#=WORKSON.E#
GROUP BY EMPLOYEE.E#;

这甚至不是完整的陈述，并给了我错误：

ERROR at line 1:
ORA-00979: not a GROUP BY expression

我可以做些什么来完成声明以包括部门编号以及我应该做什么？我应该为此使用联接吗？还是应该在 WHERE 子句中加入另一个 SELECT 语句？

表格如下：

EMPLOYEE:

SQL> SELECT * FROM EMPLOYEE;            

E#    NAME               DOB         S  SALARY SUPER    D#
----- ------------------ ----------- -- ------ -------- ---
00100 Albert             13-OCT-65   M   186.5
00110 Alvin              13-OCT-77   M   156.4 00100      1
00120 Alice              17-JUN-73   F   156.5 00100      2
00150 Bob                02-JUL-60   M   166.4 00100      3
00200 Carl               02-FEB-67   M   156.3 00100      4
00250 Douglass           14-APR-83   M   156.4 00100      5
00101 Peter              13-NOV-76   M    85.2 00110      1
00103 Ami                12-SEP-85   F    78.2 00110      1
00107 Wendy              12-SEP-88   F    68.2 00110      1
00109 Michael            12-SEP-90   M    58.2 00110      1
00125 Angela             20-NOV-90   F    56.4 00120      2
00105 Robert             15-JAN-86   M    66.2 00150      3
00136 Aban               15-JAN-90   M    55.3 00200      4
00187 Eadger             07-APR-86   M    76.5 00250      5

14 rows selected.

WORKSON:

SQL> SELECT * FROM WORKSON;

E#    P#      HOURS
----- ------- -----
00110    1001    10
00101    1001    20
00150    1002    10
00105    1002    10
00105    1003    20
00105    1004    20
00250    1004    15
00187    1004    25
00105    1005    15

DEPARTMENT:

SQL> SELECT * FROM DEPARTMENT;

D# DNAME              MANAG  MSDATE
-- ------------------ ------ ------------
 1 SALES              00110  02-JAN-12
 2 ACCOUNTING         00120  30-OCT-10
 3 GAMES              00150  01-MAR-08
 4 HUMAN RESOURCES    00200  02-JAN-13
 5 SPORTS             00250  10-MAY-10

PROJECT:

SQL> SELECT * FROM PROJECT;

    P# PTITLE             SPONSOR                D#  BUDGET
------ --- -------------- ---------------------- --- -------
  1001 Computation        Microsoft               1    25000
  1002 Study methods      Education committee     3    15000
  1003 Racing car         Cloud Pty Ltd           3   225000
  1004 Football           Football club           5    35000
  1005 Swimming           Education committee     5   125000

任何帮助将不胜感激。提前致谢！

Answer 1

您首先找到每个员工的小时数总和，然后将其加入您的主表。内联视图也可以使用。

SELECT EMPLOYEE.E#, EMPLOYEE.NAME, NVL(WORKSON_AGGR.TOTAL_HOURS,0)
FROM EMPLOYEE
  LEFT JOIN  (SELECT E#, SUM(HOURS) as TOTAL_HOURS
                FROM WORKSON
          GROUP BY E# ) WORKSON_AGGR
     ON (WORKSON_AGGR.E# = EMPLOYEE.E#)

现在，您可以轻松加入部门表了。

SELECT 
     E.E#,
     E.NAME,
     NVL(WORKSON_AGGR.TOTAL_HOURS,0),
     D.DNAME
FROM EMPLOYEE E
  LEFT JOIN  (SELECT E#, SUM(HOURS) as TOTAL_HOURS
                FROM WORKSON
             GROUP BY E# ) WORKSON_AGGR
     ON (WORKSON_AGGR.E# = E.E#)
  JOIN DEPARTMENT D ON (D.D# = E.D#)