需求是，统计每一个部门不同工种的薪水总和。
SQL> select deptno,ename,job,sal from emp;
DEPTNO ENAME JOB SAL
---------- ---------- --------- ----------
20 SMITH CLERK 800
30 ALLEN SALESMAN 1600
30 WARD SALESMAN 1250
20 JONES MANAGER 2975
30 MARTIN SALESMAN 1250
30 BLAKE MANAGER 2850
10 CLARK MANAGER 2450
20 SCOTT ANALYST 3000
10 KING PRESIDENT 5000
30 TURNER SALESMAN 1500
20 ADAMS CLERK 1100
30 JAMES CLERK 950
20 FORD ANALYST 3000
10 MILLER CLERK 1300
已选择14行。
SQL> select deptno,
nvl(sum(decode(job, 'MANAGER', sal)), 0) "s_MANAGER",
nvl(sum(decode(job, 'ANALYST', sal)), 0) "s_ANALYST",
nvl(sum(decode(job, 'CLERK', sal)), 0) "s_CLERK",
nvl(sum(decode(job, 'PRESIDENT', sal)), 0) "s_PRESIDENT",
nvl(sum(decode(job, 'SALESMAN', sal)), 0) "s_SALESMAN"
from emp
group by deptno;
DEPTNO s_MANAGER s_ANALYST s_CLERK s_PRESIDENT s_SALESMAN
---------- ---------- ---------- ---------- ----------- ----------
30 2850 0 950 0 5600
20 2975 6000 1900 0 0
10 2450 0 1300 5000 0
SQL> select deptno,
nvl(sum(case job when 'MANAGER' then sal else null end), 0) "s_MANAGER",
nvl(sum(case job when 'ANALYST' then sal else null end), 0) "s_ANALYST",
nvl(sum(case job when 'CLERK' then sal else null end), 0) "s_CLERK",
nvl(sum(case job when 'PRESIDENT' then sal else null end), 0) "s_PRESIDENT",
nvl(sum(case job when 'SALESMAN' then sal else null end), 0) "s_SALESMAN"
from emp
group by deptno;
DEPTNO s_MANAGER s_ANALYST s_CLERK s_PRESIDENT s_SALESMAN
---------- ---------- ---------- ---------- ----------- ----------
30 2850 0 950 0 5600
20 2975 6000 1900 0 0
10 2450 0 1300 5000 0
需求是查询每一个部门下的人员信息，在一行显示。在oracle 10g和11g上能够用WMSYS.WM_CONCAT，但值得注意的是此函数是undocument的函数（不是官方发布的函数），oracle不保证升级之后还会存在。
SQL> SELECT deptno, WMSYS.WM_CONCAT(ename) AS employees FROM emp GROUPBY deptno;
DEPTNO EMPLOYEES
---------- --------------------------------------
10 CLARK,MILLER,KING
20 SMITH,FORD,ADAMS,SCOTT,JONES
30ALLEN,JAMES,TURNER,BLAKE,MARTIN,WARD
Oracle 11g后，能够用listagg实现。
SQL> SELECT deptno, LISTAGG(ename, ',') WITHIN
GROUP( ORDER BY ename) AS employees
FROM emp
GROUP BY deptno;
DEPTNO EMPLOYEES
---------- ---------------------------------------
10 CLARK,KING,MILLER
20ADAMS,FORD,JONES,SCOTT,SMITH
30ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD