Question

有这两个表

DEPARTMENT

//DEPARTMENT
D#          DNAME
-------------------
1         RESEARCH
2            IT
3          SCIENCE

PROJECT

//PROJECT
P#       D#        BUDGET
-------------------------
1001     1         22500
1002     1         22500
1003     3         50000

当我执行此命令时

SELECT d.D#,DNAME,sum(budget) as "TOTAL BUDGETS" 
    FROM DEPARTMENT d,PROJECT p 
WHERE d.D# = p.D#
GROUP BY d.D#;

我认为结果将是

D#     DNAME     TOTAL BUDGETS
------------------------------
1     RESEARCH       45000
2        IT             0
3       SCIENCE      50000

但为什么我会收到此错误

//Oracle: NOT A GROUP BY EXPRESSION ERROR

Answer 1

SELECT列表中的所有列名必须出现在GROUP BY子句中，除非name仅用于聚合函数。

将查询更改为：

SELECT d.D#,DNAME,sum(budget) as "TOTAL BUDGETS" 
    FROM DEPARTMENT d,PROJECT p 
WHERE d.D# = p.D#
GROUP BY d.D#, DNAME;

评论更新：

SELECT d.D#, d.DNAME, NVL(SUM(p.budget), 0) as "TOTAL BUDGETS" 
    FROM DEPARTMENT d LEFT OUTER JOIN PROJECT p ON d.D#=p.D#
GROUP BY d.D#, d.DNAME;

Answer 2

SELECT d.D#,max(DNAME),sum(budget) as "TOTAL BUDGETS" 
    FROM DEPARTMENT d,PROJECT p 
WHERE d.D# = p.D#
GROUP BY d.D#;

您应该在GROUP BY部分中包含该字段，或者使用汇总功能（MAX或MIN可以用于此案例）

Answer 3

您忘记在 GROUP BY 语句中声明d.DNAME列：

SELECT d.D#,d.DNAME,sum(BUDGET) as "TOTAL BUDGETS" 
    FROM DEPARTMENT d,PROJECT p 
WHERE d.D# = p.D#
GROUP BY d.D#, d.DNAME;

SQLFiddle Example

如果要显示所有部门，则需要使用 LEFT JOIN

SELECT d.D#,d.DNAME,sum(BUDGET) as "TOTAL BUDGETS" 
    FROM DEPARTMENT d
LEFT JOIN PROJECT p
ON d.D# = p.D#
GROUP BY d.D#, d.DNAME;

SQLFiddle Example

如果没有项目，则显示0您需要使用 CASE 语句

SELECT d.D#,d.DNAME,
CASE WHEN sum(BUDGET) IS NULL
    THEN 0
    ELSE sum(BUDGET) END AS "TOTAL BUDGETS" 
FROM DEPARTMENT d
LEFT JOIN PROJECT p
ON d.D# = p.D#
GROUP BY d.D#, d.DNAME;

输出：

   D#   DNAME   TOTAL BUDGETS
    2   IT  0
    1   RESEARCH    45000
    3   SEARCH  50000

SQLFiddle Example

通过返回错误与组进行SUM

3 个答案: