Oracle学习02【持续更新】

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Oracle继续学习中。。。。。。

查询职位是"MANAGER"或职位不是"ANALYST"的员工（方式一）

select * from emp where job='MANAGER' or not(job='ANALYST');

SQL> select * from emp where job='MANAGER' or not(job='ANALYST');EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7369 SMITH      CLERK       7902 17-12月-80     800           20 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10 7839 KING       PRESIDENT        17-11月-81    5000           10 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7934 MILLER     CLERK       7782 23-1月 -82    1300           10已选择12行。

查询职位是"MANAGER"或职位不是"ANALYST"的员工（方式二）:select * from emp where job='MANAGER' or job!='ANALYST';

SQL> select * from emp where job='MANAGER' or job !='ANALYST';EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7369 SMITH      CLERK       7902 17-12月-80     800           20 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10 7839 KING       PRESIDENT        17-11月-81    5000           10 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7934 MILLER     CLERK       7782 23-1月 -82    1300           10已选择12行。

查询员工信息，按薪水升序排序:select * from emp order by sal desc;

SQL> select * from emp order by sal desc;EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7839 KING       PRESIDENT        17-11月-81    5000           10 7902 FORD       ANALYST     7566 03-12月-81    3000           20 7788 SCOTT      ANALYST     7566 19-4月 -87    3000           20 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7934 MILLER     CLERK       7782 23-1月 -82    1300           10 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7369 SMITH      CLERK       7902 17-12月-80     800           20已选择14行。

查询员工信息，按入职日期降序排序：select * from emp order by hiredate desc;

SQL> select * from emp order by hiredate desc;EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7788 SCOTT      ANALYST     7566 19-4月 -87    3000           20 7934 MILLER     CLERK       7782 23-1月 -82    1300           10 7902 FORD       ANALYST     7566 03-12月-81    3000           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7839 KING       PRESIDENT        17-11月-81    5000           10 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7369 SMITH      CLERK       7902 17-12月-80     800           20

已选择14行

order by后面可以跟列名、别名、表达式、列号
select * from emp order by sal desc;

select empno "编号",ename "姓名",sal "工资" from emp order by "工资" desc;

SQL> select empno "编号",ename "姓名",sal "工 资" from emp order by "工 资" desc;      编号 姓名                      工 资---------- -------------------- ----------      7839 KING                       5000      7902 FORD                       3000      7788 SCOTT                      3000      7566 JONES                      2975      7698 BLAKE                      2850      7782 CLARK                      2450      7499 ALLEN                      1600      7844 TURNER                     1500      7934 MILLER                     1300      7521 WARD                       1250      7654 MARTIN                     1250      7876 ADAMS                      1100      7900 JAMES                       950      7369 SMITH                       800已选择14行。

select empno "编号",ename "姓名",sal "工资",sal*12 "年薪" from emp order by sal*12 desc;

SQL> select empno "编号",ename "姓名",sal "工资",sal*12 "年薪" from emp order by sal*12 desc;      编号 姓名                       工资       年薪---------- -------------------- ---------- ----------      7839 KING                       5000      60000      7902 FORD                       3000      36000      7788 SCOTT                      3000      36000      7566 JONES                      2975      35700      7698 BLAKE                      2850      34200      7782 CLARK                      2450      29400      7499 ALLEN                      1600      19200      7844 TURNER                     1500      18000      7934 MILLER                     1300      15600      7521 WARD                       1250      15000      7654 MARTIN                     1250      15000      7876 ADAMS                      1100      13200      7900 JAMES                       950      11400      7369 SMITH                       800       9600已选择14行。

select empno "编号",ename "姓名",sal "工资",sal*12 "年薪" from emp order by 4 desc;

SQL> select empno "编号",ename "姓名",sal "工资",sal*12 "年薪" from emp order by 4 desc;      编号 姓名                       工资       年薪---------- -------------------- ---------- ----------      7839 KING                       5000      60000      7902 FORD                       3000      36000      7788 SCOTT                      3000      36000      7566 JONES                      2975      35700      7698 BLAKE                      2850      34200      7782 CLARK                      2450      29400      7499 ALLEN                      1600      19200      7844 TURNER                     1500      18000      7934 MILLER                     1300      15600      7521 WARD                       1250      15000      7654 MARTIN                     1250      15000      7876 ADAMS                      1100      13200      7900 JAMES                       950      11400      7369 SMITH                       800       9600已选择14行。

查询员工信息，按佣金升序或降序排列，null值放后面（nulls last）

select * from emp order by comm asc;

SQL> select * from emp order by comm asc;EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7788 SCOTT      ANALYST     7566 19-4月 -87    3000           20 7839 KING       PRESIDENT        17-11月-81    5000           10 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7902 FORD       ANALYST     7566 03-12月-81    3000           20 7934 MILLER     CLERK       7782 23-1月 -82    1300           10 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7369 SMITH      CLERK       7902 17-12月-80     800           20 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10已选择14行。

select * from emp order by comm desc nulls last;

SQL> select * from emp order by comm desc nulls last;EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7788 SCOTT      ANALYST     7566 19-4月 -87    3000           20 7839 KING       PRESIDENT        17-11月-81    5000           10 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7902 FORD       ANALYST     7566 03-12月-81    3000           20 7934 MILLER     CLERK       7782 23-1月 -82    1300           10 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7369 SMITH      CLERK       7902 17-12月-80     800           20 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10已选择14行。

查询员工信息，按工资降序排列,相同工资的员工再按入职时间降序排列

select * from emp order by sal desc,hiredate desc;

SQL> select * from emp order by sal desc,hiredate desc;EMPNO ENAME      JOB          MGR HIREDATE       SAL  COMM DEPTNO----- ---------- ---------- ----- ------------ ----- ----- ------ 7839 KING       PRESIDENT        17-11月-81    5000           10 7788 SCOTT      ANALYST     7566 19-4月 -87    3000           20 7902 FORD       ANALYST     7566 03-12月-81    3000           20 7566 JONES      MANAGER     7839 02-4月 -81    2975           20 7698 BLAKE      MANAGER     7839 01-5月 -81    2850           30 7782 CLARK      MANAGER     7839 09-6月 -81    2450           10 7499 ALLEN      SALESMAN    7698 20-2月 -81    1600   300     30 7844 TURNER     SALESMAN    7698 08-9月 -81    1500     0     30 7934 MILLER     CLERK       7782 23-1月 -82    1300           10 7654 MARTIN     SALESMAN    7698 28-9月 -81    1250  1400     30 7521 WARD       SALESMAN    7698 22-2月 -81    1250   500     30 7876 ADAMS      CLERK       7788 23-5月 -87    1100           20 7900 JAMES      CLERK       7698 03-12月-81     950           30 7369 SMITH      CLERK       7902 17-12月-80     800           20已选择14行。

测试LOWER/UPPER/INITCAP函数
select lower('Hello World') "转小写",upper('Hello World') "转大写",initcap('hello world') "首字母大写" from dual;

SQL> select lower('Hello World') "转小写",upper('Hello World') "转大写",initcap('hello world') "首字母大写" from dual;转小写                 转大写                 首字母大写---------------------- ---------------------- ----------------------hello world            HELLO WORLD            Hello World

测试CONCAT/SUBSTR函数，从1开始：
select concat('hello',' world') "字符串拼接",substr('hello world',7,11) "字符串截取" from dual;

SQL> select concat('hello',' world') "字符串拼接",substr('hello world',7,11) "字符串截取" from dual;字符串拼接             字符串截取---------------------- ----------hello world            world

测试LENGTH/LENGTHB函数：

select length('中CHINA') "字符",lengthb('中CHINA') "字节" from dual;

SQL> select length('中CHINA') "字符",lengthb('中CHINA') "字节" from dual;

      字符       字节---------- ----------         6          8

length：不管中英文，都是1位

lengthb：英文，是1位；中文是3位【unicode即utf-8】
测试INSTR/LPAD/RPAD函数

SQL> select instr('hello world','o'),lpad('haha',10,'#'),rpad('hehe',10,'@') from dual;INSTR('HELLOWORLD','O') LPAD('HAHA',10,'#')  RPAD('HEHE',10,'@')----------------------- -------------------- --------------------                      5 ######haha           hehe@@@@@@

测试TRIM/REPLACE函数

select trim('x' from 'xxxHELLOxxxWORLDxxx'),replace('abcd','c','$') from dual;

SQL> select trim('x' from 'xxxHELLOxxxWORLDxxx'),replace('abcd','c','$') from dual;TRIM('X'FROM'XXXHELLOXXXWO REPLACE(-------------------------- --------HELLOxxxWORLD              ab$d

select trim(' ' from ' HELLO WORLD ') from dual;

SQL> select trim(' ' from '   HELLO   WORLD   ') from dual;TRIM(''FROM'HELLOWORLD')--------------------------HELLO   WORLD

测试ROUND/TRUNC/MOD函数
select round(3.1415926,3),trunc(3.1415926,3),mod(1000,300) from dual;

SQL> select round(3.1415926,3),trunc(3.1415926,3),mod(1000,300) from dual;ROUND(3.1415926,3) TRUNC(3.1415926,3) MOD(1000,300)------------------ ------------------ -------------             3.142              3.141           100

select round(sysdate,'month') from dual;

SQL> select round(sysdate,'month') from dual;ROUND(SYSDATE,--------------01-7月 -16

select trunc(sysdate,'month') from dual;

SQL> select trunc(sysdate,'month') from dual;TRUNC(SYSDATE,--------------01-6月 -16

显示昨天，今天，明天的日期
select sysdate-1 "昨天",sysdate "今天",sysdate+1 明天 from dual;

SQL> select sysdate-1 "昨天",sysdate "今天",sysdate+1 明天 from dual;昨天           今天           明天-------------- -------------- --------------19-6月 -16     20-6月 -16     21-6月 -16

以年和月形式显示员工近似工龄
select ename "姓名",sysdate-hiredate "日工龄",(sysdate-hiredate)/30 "月工龄",(sysdate-hiredate)/365 "年工龄" from emp;

SQL> select ename "姓名",sysdate-hiredate "日工龄",(sysdate-hiredate)/30 "月工龄",(sysdate-hiredate)/365 "年工龄" from emp;姓名                     日工龄     月工龄     年工龄-------------------- ---------- ---------- ----------SMITH                 12969.987 432.332899 35.5342109ALLEN                 12904.987 430.166232 35.3561287WARD                  12902.987 430.099566 35.3506492JONES                 12863.987 428.799566 35.2437999MARTIN                12684.987 422.832899  34.753389BLAKE                 12834.987 427.832899 35.1643479CLARK                 12795.987 426.532899 35.0574985SCOTT                 10655.987 355.199566 29.1944848KING                  12634.987 421.166232 34.6164027TURNER                12704.987 423.499566 34.8081835ADAMS                 10621.987 354.066232 29.1013342JAMES                 12618.987 420.632899  34.572567FORD                  12618.987 420.632899  34.572567MILLER                12567.987 418.932899  34.432841已选择14行。

使用MONTHS_BETWEEN函数，以精确月形式显示员工工龄
select ename "姓名",(sysdate-hiredate)/30 "近似月工龄",months_between(sysdate,hiredate) "精确月工龄" from emp;

SQL> select ename "姓名",(sysdate-hiredate)/30 "近似月工龄",months_between(sysdate,hiredate) "精确月工龄" from emp;姓名                 近似月工龄 精确月工龄-------------------- ---------- ----------SMITH                432.332915 426.128627ALLEN                430.166248        424WARD                 430.099581 423.967337JONES                428.799581 422.612498MARTIN               422.832915 416.773788BLAKE                427.832915 421.644756CLARK                426.532915 420.386692SCOTT                355.199581 350.064111KING                 421.166248 415.128627TURNER               423.499581  417.41895ADAMS                354.066248 348.935079JAMES                420.632915  414.58024FORD                 420.632915  414.58024MILLER               418.932915 412.935079已选择14行。

测试ADD_MONTHS函数

select add_months(sysdate,3) from dual;

SQL> select add_months(sysdate,3) from dual;ADD_MONTHS(SYS--------------20-9月 -16

测试NEXT_DAY函数【中文平台】

select next_day(sysdate,'星期三') from dual;

SQL> select next_day(sysdate,'星期三') from dual;NEXT_DAY(SYSDA--------------22-6月 -16

从今天开始算，下一个星期三是多少号？

select next_day(next_day(sysdate,'星期三'),'星期三') from dual;

SQL> select next_day(next_day(sysdate,'星期三'),'星期三') from dual;NEXT_DAY(NEXT_--------------29-6月 -16

日期隐式转换，读字符串，判断是否符合日期格式要求，再隐式转换，效率低
select ename,hiredate from emp where hiredate='17-12月-80';
隐式转换
'123'字符串-->123数值
'1-1月-13'--->1-1月-13
123---------->'123'
1-1月-13----->'1-1月-13'
日期显式转换，效率高，项目中提倡使用
select ename,to_char(hiredate,'yyyy-mm-dd') from emp where hiredate=to_date('1980-12-17','yyyy-mm-dd');

SQL> select ename,to_char(hiredate,'yyyy-mm-dd') from emp where hiredate=to_date('1980-12-17','yyyy-mm-dd');ENAME      TO_CHAR(HIREDATE,'YY---------- --------------------SMITH      1980-12-17

使用to_char()函数将日期转成字符串，显示如下格式：2012-12-1 今天是星期六 20:12:47
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;

SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;TO_CHAR(SYSDATE,'YYYY-MM-DDHH24:MI:SS'--------------------------------------2016-06-20 23:48:23

select to_char(sysdate,'YYYY-MM-DD-DAY HH:MI:SS AM')from dual;

SQL> select to_char(sysdate,'YYYY-MM-DD-DAY HH:MI:SS AM')from dual;TO_CHAR(SYSDATE,'YYYY-MM-DD-DAYHH:MI:SSAM')--------------------------------------------------------------------2016-06-20-星期一 11:50:02 下午

select to_char(sysdate,'yyyy-mm-dd "今天是" day hh24:mi:ss') "时间"from dual;
常量一定要用""双引号定界

SQL> select to_char(sysdate,'yyyy-mm-dd "今天是" day hh24:mi:ss') "时间"from dual;时间--------------------------------------------------------------------------------2016-06-20 今天是 星期一 23:50:35

显示员工工资，加上$或￥符号和千位符
select ename,to_char(sal,'$9,999') from emp;
select ename,to_char(sal,'L9,999') from emp;

SQL> select ename,to_char(sal,'$9,999') from emp;ENAME      TO_CHAR(SAL,'$---------- --------------SMITH         $800ALLEN       $1,600WARD        $1,250JONES       $2,975MARTIN      $1,250BLAKE       $2,850CLARK       $2,450SCOTT       $3,000KING        $5,000TURNER      $1,500ADAMS       $1,100JAMES         $950FORD        $3,000MILLER      $1,300已选择14行。

SQL> select ename,to_char(sal,'L9,999') from emp;ENAME      TO_CHAR(SAL,'L9,999')---------- --------------------------------SMITH                ￥800ALLEN              ￥1,600WARD               ￥1,250JONES              ￥2,975MARTIN             ￥1,250BLAKE              ￥2,850CLARK              ￥2,450SCOTT              ￥3,000KING               ￥5,000TURNER             ￥1,500ADAMS              ￥1,100JAMES                ￥950FORD               ￥3,000MILLER             ￥1,300已选择14行。

使用to_number()函数将字符串转成数字
select to_number('123')+100 "结果" from dual;

SQL> select to_number('123')+100 "结果" from dual;      结果----------       223

使用nul函数，统计员工年收入
select ename,12*sal+nvl(comm,0) from emp;

SQL> select ename,12*sal+nvl(comm,0) from emp;ENAME      12*SAL+NVL(COMM,0)---------- ------------------SMITH                    9600ALLEN                   19500WARD                    15500JONES                   35700MARTIN                  16400BLAKE                   34200CLARK                   29400SCOTT                   36000KING                    60000TURNER                  18000ADAMS                   13200JAMES                   11400FORD                    36000MILLER                  15600已选择14行。

使用nul2函数，统计员工年收入
使用nullif函数，比较10和10.0是否相同
select nullif(10,10.0)from dual;

使用case表达式，职位是总载的，工资+1000；职位是经理的，工资+800；职位是其它的，工资+400
select ename,job,sal,
case job
when 'PRESIDENT' then sal+1000
when 'MANAGER' then sal+800
else sal+400
end "涨后薪水"

from emp;

SQL> select ename,job,sal,  2         case job  3              when 'PRESIDENT' then sal+1000  4              when 'MANAGER'   then sal+800  5              else  sal+400  6         end "涨后薪水"  7  from emp;ENAME      JOB          SAL   涨后薪水---------- ---------- ----- ----------SMITH      CLERK        800       1200ALLEN      SALESMAN    1600       2000WARD       SALESMAN    1250       1650JONES      MANAGER     2975       3775MARTIN     SALESMAN    1250       1650BLAKE      MANAGER     2850       3650CLARK      MANAGER     2450       3250SCOTT      ANALYST     3000       3400KING       PRESIDENT   5000       6000TURNER     SALESMAN    1500       1900ADAMS      CLERK       1100       1500JAMES      CLERK        950       1350FORD       ANALYST     3000       3400MILLER     CLERK       1300       1700已选择14行。

各数据库厂都支持ANSISQL标准
使用decode函数，职位是总载的，工资+1000；职位是经理的，工资+800；职位是其它的，工资+400
select ename,job,sal 涨前薪水,
decode(job,'PRESIDENT',sal+1000,'MANAGER',sal+800,sal+400) "涨后薪水" from emp;
decode函数专用

SQL> select ename,job,sal 涨前薪水,  2         decode(job,'PRESIDENT',sal+1000,'MANAGER',sal+800,sal+400) "涨后薪水" from emp;ENAME      JOB          涨前薪水   涨后薪水---------- ---------- ---------- ----------SMITH      CLERK             800       1200ALLEN      SALESMAN         1600       2000WARD       SALESMAN         1250       1650JONES      MANAGER          2975       3775MARTIN     SALESMAN         1250       1650BLAKE      MANAGER          2850       3650CLARK      MANAGER          2450       3250SCOTT      ANALYST          3000       3400KING       PRESIDENT        5000       6000TURNER     SALESMAN         1500       1900ADAMS      CLERK            1100       1500JAMES      CLERK             950       1350FORD       ANALYST          3000       3400MILLER     CLERK            1300       1700已选择14行。

员工总工资，平均工资
select sum(sal) "总工资",round(avg(sal),2) "平均工资" from emp;

SQL> select sum(sal) "总工资",round(avg(sal),2) "平均工资" from emp;    总工资   平均工资---------- ----------     29025    2073.21

员工最高工资，最低工资
select max(sal) "最高工资",min(sal) "最低工资" from emp;

SQL> select max(sal) "最高工资",min(sal) "最低工资" from emp;  最高工资   最低工资---------- ----------      5000        800

入职最早员工，入职最晚员工
select max(hiredate) "最晚入职员工",min(hiredate) "最早入职员工" from emp;

SQL> select max(hiredate) "最晚入职员工",min(hiredate) "最早入职员工" from emp;最晚入职员工   最早入职员工-------------- --------------23-5月 -87     17-12月-80

求员工总人数
select count(*) 员工总人数 from emp;

SQL> select count(*) 员工总人数 from emp;员工总人数----------        14

统计有佣金的员工人数

select count(comm) 有佣金的员工人数 from emp;

SQL> select count(comm) 有佣金的员工人数 from emp;有佣金的员工人数----------------               4

分组函数不统计null值
统计公司有多少个部门

SQL> select count(distinct deptno) from emp;COUNT(DISTINCTDEPTNO)---------------------                    3

按部门求出部门平均工资
--以下SQL语句是正确
select deptno,trunc(avg(sal),0) from emp group by deptno;

SQL> select deptno,trunc(avg(sal),0) from emp group by deptno;DEPTNO TRUNC(AVG(SAL),0)------ -----------------    30              1566    20              2175    10              2916

select trunc(avg(sal),0) from emp group by deptno;

SQL> select trunc(avg(sal),0) from emp group by deptno;TRUNC(AVG(SAL),0)-----------------             1566             2175             2916

--以下SQL语句是错误，原因在于select子句中的非组函数没有全部出现在group by子句中
select ename,deptno,trunc(avg(sal),0)
from emp
group by ename;

查询部门平均工资大于2000元的部门
select deptno,trunc(avg(sal),0) "部门平均工资"
from emp
group by deptno
having trunc(avg(sal),0)>2000;

SQL> select deptno,trunc(avg(sal),0) "部门平均工资"  2  from emp  3  group by deptno  4  having trunc(avg(sal),0)>2000;DEPTNO 部门平均工资------ ------------    20         2175    10         2916

除10号部门外，查询部门平均工资大于2000元的部门
方式一
select deptno,trunc(avg(sal),0) "部门平均工资"
from emp
group by deptno
having trunc(avg(sal),0)>2000 and deptno!=10;

SQL> select deptno,trunc(avg(sal),0) "部门平均工资"  2  from emp  3  group by deptno  4  having trunc(avg(sal),0)>2000 and deptno!=10;DEPTNO 部门平均工资------ ------------    20         2175

方式二【先行过滤，再组过滤，性能较佳】
select deptno,trunc(avg(sal),0) "部门平均工资"
from emp
where deptno!=10
group by deptno
having trunc(avg(sal),0)>2000;

SQL> select deptno,trunc(avg(sal),0) "部门平均工资"  2  from emp  3  where deptno!=10  4  group by deptno  5  having trunc(avg(sal),0)>2000;DEPTNO 部门平均工资------ ------------    20         2175

显示部门平均工资的最大值
select max(avg(sal))
from emp

group by deptno;

SQL> select max(avg(sal))  2  from emp  3  group by deptno;MAX(AVG(SAL))-------------   2916.66667

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