Oralce透视行列转换pivot/unpivot

试验一、行转列。查询各个部门每个工资段的人数。

with emp_dept as
 (select dname, empno,sal from emp a join dept b using (deptno))
select *
  from emp_dept
pivot (count(empno) as quantity for sal in (2450 as p2450,1300 as p1300,3000 as p3000,2975 as p2975,800 as p800))
 order by dname;

 得到结果：

   	DNAME	P2450_QUANTITY	P1300_QUANTITY	P3000_QUANTITY	P2975_QUANTITY	P800_QUANTITY
1	ACCOUNTING	1	1	0	0	0
2	RESEARCH	0	0	2	1	1
3	SALES	0	0	0	0	0

 比较

通过分组来查询

select dname, sal, count(empno)
  from emp a
  join dept b
 using (deptno)
 where sal in (2450, 1300, 300, 2975, 800)
 group by dname, sal

 得到结果

   	DNAME	SAL	COUNT(EMPNO)
1	ACCOUNTING	1300	1
2	RESEARCH	800	1
3	ACCOUNTING	2450	1
4	RESEARCH	2975	1

 

二、

多列透视

增加一个聚合，派生列数会增加一倍。

with dept_salary as
 (select dname, empno, sal from emp a, dept b where a.deptno = b.deptno)
select *
  from dept_salary
pivot (count(empno) as sal, sum(nvl(sal, 0)) as sum_prc for sal in(800 as p800,
                                                              2975 as p2975,
                                                              1250 as p1250))
order by dname;

 结果：略。