1. 分組函數只能出現在選擇列表（select），having，order by 子句中；
2.如果在select語句中同時包含有group by，having，order by，那麼，他們的優先級是，group by，having和order by
3.在選擇列種，如果有列，表達式和分組函數，那麼，這些列和表達式，必須有一個出現在group by子句中！
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------
7698 BLAKE MANAGER 7839 1981/5/1 2850.00 30
7499 ALLEN SALESMAN 7698 1981/2/20 1600.00 300.00 30
7844 TURNER SALESMAN 7698 1981/9/8 1500.00 0.00 30
7654 MARTIN SALESMAN 7698 1981/9/28 1250.00 1400.00 30
7521 WARD SALESMAN 7698 1981/2/22 1250.00 500.00 30
7900 JAMES CLERK 7698 1981/12/3 950.00 30
7788 SCOTT ANALYST 7566 1987/4/19 3000.00 20
7902 FORD ANALYST 7566 1981/12/3 3000.00 20
7566 JONES MANAGER 7839 1981/4/2 2975.00 20
7876 ADAMS CLERK 7788 1987/5/23 1100.00 20
7370 Jonny clerk 7902 1999/11/11 1000.00 20
7369 SMITH CLERK 7902 1980/12/17 800.00 20
7839 KING PRESIDENT 1981/11/17 5000.00 10
7782 CLARK MANAGER 7839 1981/6/9 2450.00 10
7934 MILLER CLERK 7782 1982/1/23 1300.00 10</pre><pre name="code" class="sql">//以年薪排序
SQL> select empno,ename,job, sal,comm, sal*12+nvl(comm,0)*12 "年薪"from emp order by "年薪" desc;
EMPNO ENAME JOB SAL COMM 年薪
----- ---------- --------- --------- --------- ----------
7839 KING PRESIDENT 5000.00 60000
7902 FORD ANALYST 3000.00 36000
7788 SCOTT ANALYST 3000.00 36000
7566 JONES MANAGER 2975.00 35700
7698 BLAKE MANAGER 2850.00 34200
7654 MARTIN SALESMAN 1250.00 1400.00 31800
7782 CLARK MANAGER 2450.00 29400
7499 ALLEN SALESMAN 1600.00 300.00 22800
7521 WARD SALESMAN 1250.00 500.00 21000
7844 TURNER SALESMAN 1500.00 0.00 18000
7934 MILLER CLERK 1300.00 15600
7876 ADAMS CLERK 1100.00 13200
7370 Jonny clerk 1000.00 12000
7900 JAMES CLERK 950.00 11400
7369 SMITH CLERK 800.00 9600//數據分組
SQL> select max(sal), min(sal) from emp;
MAX(SAL) MIN(SAL)
---------- ----------
5000 800//針對第一條的範例
SQL> select * from emp where sal=(select max(sal) from emp);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------
7839 KING PRESIDENT 1981/11/17 5000.00 10
Executed in 0.03 secondsSQL> select * from emp where sal=(select max(sal) from emp) or sal = (select min(sal) from emp);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------
7369 SMITH CLERK 7902 1980/12/17 800.00 20
7839 KING PRESIDENT 1981/11/17 5000.00 10
Executed in 0.035 seconds//針對【三】的範例
SQL> select avg(sal),max(sal), deptno from emp group by deptno;
AVG(SAL) MAX(SAL) DEPTNO
---------- ---------- ------
1566.66666 2850 30
1979.16666 3000 20
2916.66666 5000 10
Executed in 0.051 seconds//having 的用法
SQL> select avg(sal),deptno from emp group by deptno having avg(sal)<2000;
AVG(SAL) DEPTNO
---------- ------
1566.66666 30
1979.16666 20
Executed in 0.039 seconds//語句的集合
SQL> select avg(sal),max(sal),deptno from emp
2 group by deptno
3 having avg(sal)>1800
4 order by avg(sal) desc;
AVG(SAL) MAX(SAL) DEPTNO
---------- ---------- ------
2916.66666 5000 10
1979.16666 3000 20
Executed in 0.036 seconds
//group by 後跟表達式
SQL> select ename,job,sal*12+nvl(comm,0)*12 as "Subtotal Sal",avg(sal),max(sal) from emp
2 group by ename,job,sal*12+nvl(comm,0)*12;
ENAME JOB Subtotal Sal AVG(SAL) MAX(SAL)
---------- --------- ------------ ---------- ----------
JONES MANAGER 35700 2975 2975
ADAMS CLERK 13200 1100 1100
JAMES CLERK 11400 950 950
Jonny clerk 12000 1000 1000
CLARK MANAGER 29400 2450 2450
SMITH CLERK 9600 800 800
TURNER SALESMAN 18000 1500 1500
FORD ANALYST 36000 3000 3000
MARTIN SALESMAN 31800 1250 1250
ALLEN SALESMAN 22800 1600 1600
BLAKE MANAGER 34200 2850 2850
KING PRESIDENT 60000 5000 5000
MILLER CLERK 15600 1300 1300
WARD SALESMAN 21000 1250 1250
SCOTT ANALYST 36000 3000 3000
15 rows selected
Executed in 0.123 seconds<pre name="code" class="sql">
//全套
SQL> select ename,job,sal*12+nvl(comm,0)*12 as "Subtotal Sal",avg(sal),max(sal) from emp
2 group by ename,job,sal*12+nvl(comm,0)*12
3 having avg(sal)> 1000
4 order by "Subtotal Sal" desc;
ENAME JOB Subtotal Sal AVG(SAL) MAX(SAL)
---------- --------- ------------ ---------- ----------
KING PRESIDENT 60000 5000 5000
FORD ANALYST 36000 3000 3000
SCOTT ANALYST 36000 3000 3000
JONES MANAGER 35700 2975 2975
BLAKE MANAGER 34200 2850 2850
MARTIN SALESMAN 31800 1250 1250
CLARK MANAGER 29400 2450 2450
ALLEN SALESMAN 22800 1600 1600
WARD SALESMAN 21000 1250 1250
TURNER SALESMAN 18000 1500 1500
MILLER CLERK 15600 1300 1300
ADAMS CLERK 13200 1100 1100
12 rows selected
Executed in 0.098 seconds