《卸甲笔记》-分组统计查询

Posted 2020-07-30

统计函数对比

1查询出公司每个月支出的月工资总和

Oracle

SQL> select SUM(sal) from emp;

 

  SUM(SAL)

----------

     29025

PPAS

scott=# select SUM(sal) from emp;

   sum   

----------

 29025.00

(1 row)

2查询出公司的最高工资，最低工资，平均工资

Oracle

SQL> select AVG(sal),ROUND(AVG(sal),2),MAX(sal),MIN(sal) from emp;

 

  AVG(SAL) ROUND(AVG(SAL),2)   MAX(SAL)   MIN(SAL)

---------- ----------------- ---------- ----------

2073.21429           2073.21    5000        800

PPAS

scott=# select AVG(sal),ROUND(AVG(sal),2),MAX(sal),MIN(sal) from emp;

          avg          |  round  |   max   |  min  

-----------------------+---------+---------+--------

 2073.2142857142857143 | 2073.21 | 5000.00 | 800.00

(1 row)

3统计出公司最早雇佣和最晚雇佣的雇佣日期

Oracle

SQL> select MIN(hiredate) 最早雇佣日期,MAX(hiredate) 最晚雇佣日期 from emp;

 

最早雇佣日期 最晚雇佣日期

------------ ------------

17-DEC-80    23-MAY-87

 

PPAS

scott=# select MIN(hiredate) 最早雇佣日期,MAX(hiredate) 最晚雇佣日期 from emp;

    最早雇佣日期    |    最晚雇佣日期   

--------------------+--------------------

 17-DEC-80 00:00:00 | 23-MAY-87 00:00:00

(1 row)

4统计公司中间的工资值

Oracle

SQL> select MEDIAN(sal) from emp;

 

MEDIAN(SAL)

-----------

       1550

 

PPAS

PPAS中没有求中位数的函数

5统计工资的标准差与方差

Oracle

SQL> select STDDEV(sal),VARIANCE(sal) from emp;

 

STDDEV(SAL) VARIANCE(SAL)

----------- -------------

 1182.50322    1398313.87

PPAS

scott=# select STDDEV(sal),VARIANCE(sal) from emp;

      stddev       |       variance      

-------------------+----------------------

 1182.503223516272 | 1398313.873626373626

(1 row)

6统计出公司的雇员人数

Oracle

SQL> select COUNT(empno),COUNT(*) from emp;

 

COUNT(EMPNO)   COUNT(*)

------------ ----------

           14              14

PPAS

scott=# select COUNT(empno),COUNT(*) from emp;

 count | count

-------+-------

    14 |    14

(1 row)

7验证COUNT(*)、COUNT(字段)、COUNT(DISTINCT 字段)的使用区别

Oracle

SQL>  select COUNT(*),COUNT(ename),COUNT(comm),COUNT(DISTINCT job) from emp;

 

  COUNT(*) COUNT(ENAME) COUNT(COMM) COUNT(DISTINCTJOB)

---------- ------------ ----------- ------------------

         14          14            4                 5

PPAS

scott=# select COUNT(*),COUNT(ename),COUNT(comm),COUNT(DISTINCT job) from emp;

 count | count | count | count

-------+-------+-------+-------

    14 |    14 |     4 |     5

(1 row)

8验证3中COUNT()函数的使用方式

Oracle

SQL> select COUNT(ename),AVG(sal),SUM(sal),MAX(sal),MIN(sal) from bonus;

 

COUNT(ENAME)   AVG(SAL)   SUM(SAL)   MAX(SAL)      MIN(SAL)

------------ ---------- ---------- ---------- ----------

            0

PPAS

scott=# select COUNT(ename),AVG(sal),SUM(sal),MAX(sal),MIN(sal) from bonus;

 count | avg | sum | max | min

-------+-----+-----+-----+-----

     0 |     |     |     |   

(1 row)

单字段分钟统计

9统计出每个部门的人数

Oracle

SQL> select deptno,COUNT(*)

  2  from emp

  3  GROUP BY deptno;

 

DEPTNO   COUNT(*)

---------- ----------

         30         6

         20         5

         10         3

PPAS

scott=# select deptno,COUNT(*)

scott-# from emp

scott-# GROUP BY deptno;

 deptno | count

--------+-------

     20 |     5

     30 |     6

     10 |     3

(3 rows)

10统计出每种职位的最低工资和最高工资

Oracle

SQL> select job,MIN(sal),MAX(sal)

  2  from emp

  3  GROUP BY job;

 

JOB       MIN(SAL)        MAX(SAL)

---------- ---------- ----------

CLERK                  800           1300

SALESMAN       1250           1600

PRESIDENT       5000           5000

MANAGER       2450           2975

ANALYST           3000           3000

PPAS

scott=# select job,MIN(sal),MAX(sal)

scott-# from emp

scott-# GROUP BY job;

    job    |   min   |   max  

-----------+---------+---------

 SALESMAN  | 1250.00 | 1600.00

 CLERK     |  800.00 | 1300.00

 MANAGER   | 2450.00 | 2975.00

 PRESIDENT | 5000.00 | 5000.00

 ANALYST   | 3000.00 | 3000.00

(5 rows)

11在没有分组语句（GROUP BY）时使用统计函数后出现其他字段

Oracle

SQL> select deptno,COUNT(EMPNO) from emp;

select deptno,COUNT(EMPNO) from emp

       *

ERROR at line 1:

ORA-00937: not a single-group group function

PPAS

scott=# select deptno,COUNT(EMPNO) from emp;

ERROR:  column "emp.deptno" must appear in the GROUP BY clause or be used in an aggregate function

LINE 1: select deptno,COUNT(EMPNO) from emp;

12在没有分组的时候只允许单独使用统计函数

Oracle

SQL>  select COUNT(empno) from emp;

 

COUNT(EMPNO)

------------

           14

PPAS

scott=# select COUNT(empno) from emp;

 count

-------

    14

(1 row)

13在分组查询的SELECT子句中出现其他字段（ename）

Oracle

SQL> select deptno,ename,COUNT(empno)

  2  from emp

  3  GROUP  BY deptno;

select deptno,ename,COUNT(empno)

              *

ERROR at line 1:

ORA-00979: not a GROUP BY expression

PPAS

scott=# select deptno,ename,COUNT(empno)

scott-# from emp

scott-# GROUP  BY deptno;

ERROR:  column "emp.ename" must appear in the GROUP BY clause or be used in an aggregate function

LINE 1: select deptno,ename,COUNT(empno)

14在SELECT子句之后只出现分组字段和统计函数

Oracle

SQL> select deptno,COUNT(empno)

  2  from emp

  3  GROUP BY deptno;

 

    DEPTNO COUNT(EMPNO)

---------- ------------

         30           6

         20           5

         10           3

PPAS

scott=# select deptno,COUNT(empno)

scott-# from emp

scott-# GROUP BY deptno;

 deptno | count

--------+-------

     20 |     5

     30 |     6

     10 |     3

(3 rows)

15求出每个部门平均工资最高的工资

Oracle

SQL> select MAX(AVG(sal)) from emp GROUP BY deptno;

 

MAX(AVG(SAL))

-------------

   2916.66667s

PPAS

PPAS不支持聚合函数嵌套

scott=# select MAX(AVG(sal)) from emp GROUP BY deptno;

ERROR:  aggregate function calls cannot be nested

LINE 1: select MAX(AVG(sal)) from emp GROUP BY deptno;

16错误的语句

Oracle

SQL> select deptno,MAX(AVG(sal)) from emp GROUP BY deptno;

select deptno,MAX(AVG(sal)) from emp GROUP BY deptno

       *

ERROR at line 1:

ORA-00937: not a single-group group function

PPAS

scott=# select deptno,MAX(AVG(sal)) from emp GROUP BY deptno;

ERROR:  aggregate function calls cannot be nested

LINE 1: select deptno,MAX(AVG(sal)) from emp GROUP BY deptno;

17统计函数嵌套分析

Oracle

SQL> select deptno,SUM(sal) from emp GROUP BY deptno;

 

    DEPTNO   SUM(SAL)

---------- ----------

         30     9400

         20     10875

         10     8750

PPAS

scott=# select deptno,SUM(sal) from emp GROUP BY deptno;

 deptno |   sum   

--------+----------

     20 | 10875.00

     30 |  9400.00

     10 |  8750.00

(3 rows)

18查询每个部门的名称、部门人数、部门平均工资、平均服务年限

Oracle

SQL> select d.dname,COUNT(e.empno),ROUND(AVG(e.sal),2) avgsal,

  2  ROUND(AVG(MONTHS_BETWEEN(SYSDATE,e.hiredate)/12),2) avgyear

  3   from dept d,emp e

  4  where e.deptno(+)=d.deptno

  5  GROUP BY d.dname;

 

DNAME             COUNT(E.EMPNO)     AVGSAL    AVGYEAR

--------------- -------------- ---------- ----------

ACCOUNTING                3       2916.67      34.69

OPERATIONS                  0

RESEARCH                      5          2175      32.71

SALES                               6       1566.67      34.99

PPAS

scott=# select d.dname,COUNT(e.empno),ROUND(AVG(e.sal),2) avgsal,

scott-# ROUND(AVG(MONTHS_BETWEEN(SYSDATE,e.hiredate)/12),2) avgyear

scott-# from dept d,emp e

scott-# where e.deptno(+)=d.deptno

scott-# GROUP BY d.dname;

   dname    | count | avgsal  | avgyear

------------+-------+---------+---------

 ACCOUNTING |     3 | 2916.67 |   34.69

 RESEARCH   |     5 | 2175.00 |   32.71

 OPERATIONS |     0 |         |       

 SALES      |     6 | 1566.67 |   34.98

(4 rows)

19查询公司各个工资等级雇员的数量、平均工资

Oracle

SQL> select s.grade,COUNT(e.empno),ROUND(AVG(e.sal),2)

  2  from emp e,salgrade s

  3  where e.sal between s.losal and s.hisal

  4  GROUP BY s.grade;

 

     GRADE COUNT(E.EMPNO) ROUND(AVG(E.SAL),2)

---------- -------------- -------------------

          1              3                  950

          2              3             1266.67

          4              5                2855

          5              1                5000

          3              2                1550

PPAS

scott=# select s.grade,COUNT(e.empno),ROUND(AVG(e.sal),2)

scott-# from emp e,salgrade s

scott-# where e.sal between s.losal and s.hisal

scott-# GROUP BY s.grade;

 grade | count |  round 

-------+-------+---------

     5 |     1 | 5000.00

     1 |     3 |  950.00

     3 |     2 | 1550.00

     4 |     5 | 2855.00

     2 |     3 | 1266.67

(5 rows)

20统计出领取佣金与不领取佣金的雇员的平均工资、平均雇佣年限，雇员人数

Oracle

SQL> select ‘不领取佣金‘,ROUND(AVG(sal),2) avgsal,

  2  ROUND(AVG(MONTHS_BETWEEN(SYSDATE,hiredate)/12),2) avgyear,

  3  COUNT(empno) count

  4  from emp

  5  where comm IS NOT NULL

  6  UNION

  7  select ‘领取佣金‘,ROUND(AVG(sal),2) avgsal,

  8  ROUND(AVG(MONTHS_BETWEEN(SYSDATE,hiredate)/12),2) avgyear,

  9  COUNT(empno) count

 10  from emp

 11  where comm IS NULL;

 

‘不领取佣金‘                        AVGSAL    AVGYEAR         COUNT

------------------------------ ---------- ---------- ----------

不领取佣金                            1400      35.05       4

领取佣金                               2342.5      33.73       10

PPAS

scott=# select ‘不领取佣金‘,ROUND(AVG(sal),2) avgsal,

scott-# ROUND(AVG(MONTHS_BETWEEN(SYSDATE,hiredate)/12),2) avgyear,

scott-# COUNT(empno) count

scott-# from emp

scott-# where comm IS NOT NULL

scott-# UNION

scott-# select ‘领取佣金‘,ROUND(AVG(sal),2) avgsal,

scott-# ROUND(AVG(MONTHS_BETWEEN(SYSDATE,hiredate)/12),2) avgyear,

scott-# COUNT(empno) count

scott-# from emp

scott-# where comm IS NULL;

  ?column?  | avgsal  | avgyear | count

------------+---------+---------+-------

 不领取佣金 | 1400.00 |   35.05 |     4

 领取佣金   | 2342.50 |   33.73 |    10

(2 rows)

多字段分组统计

21查询出每个部门的详细信息

Oracle

SQL> select d.deptno,d.dname,d.loc,

  2  NVL(COUNT(e.empno),0) count,NVL(ROUND(AVG(sal),2),0) avg,

  3  NVL(SUM(sal),0) sum,NVL(MAX(sal),0) max,NVL(MIN(sal),0) min

  4  from emp e,dept d

  5  where e.deptno(+)=d.deptno

  6  GROUP BY d.deptno,d.dname,d.loc;

 

    DEPTNO DNAME        LOC                COUNT       AVG    SUM         MAX     MIN

---------- --------------- ---------- ---------- ---------- ---------- ---------- ----------

         20 RESEARCH     DALLAS              5       2175  10875          3000       800

         40 OPERATIONS          BOSTON            0           0       0              0          0

         10 ACCOUNTING        NEW YORK        3    2916.67     8750          5000       1300

         30 SALES     CHICAGO          6    1566.67     9400          2850       950

PPAS

scott=# select d.deptno,d.dname,d.loc,

scott-# NVL(COUNT(e.empno),0) count,NVL(ROUND(AVG(sal),2),0) avg,

scott-# NVL(SUM(sal),0) sum,NVL(MAX(sal),0) max,NVL(MIN(sal),0) min

scott-# from emp e,dept d

scott-# where e.deptno(+)=d.deptno

scott-# GROUP BY d.deptno,d.dname,d.loc;

 deptno |   dname    |   loc    | count |   avg   |   sum    |   max   |   min  

--------+------------+----------+-------+---------+----------+---------+---------

     10 | ACCOUNTING | NEW YORK |     3 | 2916.67 |  8750.00 | 5000.00 | 1300.00

     30 | SALES      | CHICAGO  |     6 | 1566.67 |  9400.00 | 2850.00 |  950.00

     40 | OPERATIONS | BOSTON   |     0 |       0 |        0 |       0 |       0

     20 | RESEARCH   | DALLAS   |     5 | 2175.00 | 10875.00 | 3000.00 |  800.00

(4 rows)

HAVING子句

22查询出所有平均工资大于2000元的职位信息，平均工资，雇员人数

Oracle

SQL> select job,ROUND(AVG(sal),2),COUNT(empno)

  2  from emp

  3  GROUP BY job

  4  HAVING AVG(sal)>2000;

 

JOB     ROUND(AVG(SAL),2) COUNT(EMPNO)

---------- ----------------- ------------

PRESIDENT                5000                   1

MANAGER           2758.33          3

ANALYST                   3000                   2

PPAS

scott=# select job,ROUND(AVG(sal),2),COUNT(empno)

scott-# from emp

scott-# GROUP BY job

scott-# HAVING AVG(sal)>2000;

    job    |  round  | count

-----------+---------+-------

 MANAGER   | 2758.33 |     3

 PRESIDENT | 5000.00 |     1

 ANALYST   | 3000.00 |     2

(3 rows)

23列出至少有一个员工的所有部门编号、名称，并统计出这些部门的平均工资、最低工资，最高工资

Oracle

SQL> select d.deptno,d.dname,ROUND(AVG(e.sal),2),MIN(e.sal),MAX(e.sal)

  2  from emp e,dept d

  3  where e.deptno(+)=d.deptno

  4  GROUP BY d.deptno,d.dname,d.loc

  5  HAVING COUNT(e.empno)>1;

 

    DEPTNO DNAME        ROUND(AVG(E.SAL),2) MIN(E.SAL) MAX(E.SAL)

---------- --------------- ------------------- ---------- ----------

         20 RESEARCH                       2175           800       3000

         10 ACCOUNTING                     2916.67           1300       5000

         30 SALES                  1566.67            950       2850

 

PPAS

scott=# select d.deptno,d.dname,ROUND(AVG(e.sal),2),MIN(e.sal),MAX(e.sal)

scott-# from emp e,dept d

scott-# where e.deptno(+)=d.deptno

scott-# GROUP BY d.deptno,d.dname,d.loc

scott-# HAVING COUNT(e.empno)>1;

 deptno |   dname    |  round  |   min   |   max  

--------+------------+---------+---------+---------

     10 | ACCOUNTING | 2916.67 | 1300.00 | 5000.00

     30 | SALES      | 1566.67 |  950.00 | 2850.00

     20 | RESEARCH   | 2175.00 |  800.00 | 3000.00

(3 rows)

24显示非销售人员工作名称以及从事同一工作雇员的月工资的总和，并且要满足从事同一工作的雇员的月工资合计大于5000元，输出结果按月工资的合计升序排列

Oracle

SQL> select job,SUM(sal) sum

  2  from emp

  3  where job <> ‘SALESMAN‘

  4  GROUP BY job

  5  HAVING SUM(sal)>5000

  6  ORDER BY sum ASC;

 

JOB             SUM

---------- ----------

ANALYST           6000

MANAGER       8275

PPAS

scott=# select job,SUM(sal) sum

scott-# from emp

scott-# where job <> ‘SALESMAN‘

scott-# GROUP BY job

scott-# HAVING SUM(sal)>5000

scott-# ORDER BY sum ASC;

   job   |   sum  

---------+---------

 ANALYST | 6000.00

 MANAGER | 8275.00

(2 rows)