Question

我有两张桌子

CREATE TABLE DBTEST.EMP
(
  EMP_ID   NUMBER,
  NAME     VARCHAR2(20 BYTE),
  SALARY   NUMBER,
  DEPT_ID  NUMBER,
  LOC_ID   NUMBER
)

CREATE TABLE DBTEST.LOC
(
  LOC_ID       NUMBER,
  CODE         VARCHAR2(3 BYTE),
  DESCRIPTION  VARCHAR2(100 BYTE)
)

示例数据

EMP_ID  NAME        SALARY  DEPT_ID LOC_ID
1       Timmins     180000  1       1
2       Lauchnor    180000  1       1
4       Anderson            4       1
11      Pitcher     116000  3       2
17      Hedrick     182000  3       2
25      Mandurino   182000  2       1
69      Frenzel     62000   4       3



LOC_ID  CODE    DESCRIPTION
1       UT      Utah
2       CA      California
3       EU      Europe

我想列出工资低于平均水平的员工？注意：这是一组示例。

我希望你理解它。

由于

Answer 1

这样的事情怎么样？

Select emp.*
  From DBTEST.EMP emp,
    (Select Avg(Salary) avg_salary, loc_id From DBTEST.EMP Group By LOC_ID) averages
  Where averages.loc_id = emp.loc_id
    And emp.salary < averages.avg_salary;

这符合您使用Group By的要求，但如果给予选择，我会没有这样做，如下：

Select *
  From DBTEST.EMP emp
  Where salary <
    (Select Avg(salary) From DBTEST.EMP emp2 Where emp2.loc_id = emp.loc_id);

这已经过测试，两个查询都会返回以下内容：

"EMP_ID","NAME","SALARY","DEPT_ID","LOC_ID"
"2","Lauchnor","180000","1","1"
"1","Timmins","180000","1","1"
"11","Pitcher","116000","3","2"

Answer 2

在这种情况下，使用AVG()作为窗口函数（Oracle术语中的分析函数）可能更容易：

SELECT * FROM (
    SELECT emp_id, name, salary
         , dept_id, loc_id
         , AVG(salary) OVER ( PARTITION BY loc_id ) AS avg_salary
      FROM emp
) WHERE salary < avg_salary;

Please refer to SQL Fiddle demo here.

Oracle SQL查询使用group by子句

2 个答案: