行列转化

--case when 的行转列
select e.job as "工作"，
case e.deptno when 10 then sal end as " 部门 10 工资",
case e.deptno when 20 then sal end as "部门 20 工资",
case e.deptno when 30 then sal end as "部门 30 工资",
e.sal as "合计工资"
from emp e order by 1

--通过工作岗位分组
select e.job as "工作"， sum(case e.deptno
when 10 then
sal
end) as " 部门 10 工资",
sum(case e.deptno
when 20 then
sal
end) as "部门 20 工资",
sum(case e.deptno
when 30 then
sal
end) as "部门 30 工资", sum(e.sal) as "合计工资"
from emp e
group by job
order by 1

--PVIOT
select *
from (select job, sal, deptno from emp)
pivot(sum(sal) as sal
for deptno in(10 as d10, 20 as d20, 30 as d30))
order by 1
--PIVOT只能按一个条件来完成"行转列”，如果同时把工作与部门都转为列，加以汇总时，PIVOT就无能为力了，
--只能用case when
select count(case
when deptno = 10 then
ename
end) as deptno_10,
count(case
when deptno = 20 then
ename
end) as deptno_20,
count(case
when deptno = 30 then
ename
end) as deptno_30,
count(case
when job = 'CLERK' then
ename
end) as clerks,
count(case
when job = 'MANAGER' then
ename
end) as MANAGER,
count(case
when job = 'PRESIDENT' then
ename
end) as PRESIDENT,
count(case
when job = 'ANALYST' then
ename
end) as ANALYST,
count(case
when job = 'SALESMAN' then
ename
end) as SALESMAN
from emp
--列转行
create table test as
select *
from (select deptno, sal from emp)
pivot(count(1) as cnt, sum(sal) as sal
for deptno in(10 as deptno_10, 20 as deptno_20, 30 as deptno_30))
order by 1
--需求把3个部门的人次显示为一列,比较笨写法。
select '10' as "部门编码", deptno_10_cnt as "人次"
from test
union all
select '20' as "部门编码", deptno_20_cnt as "人次"
from test
union all
select '30' as "部门编码", deptno_30_cnt as "人次"
from test
--用unpivot
select deptno as 列名, substr(deptno, -6, 2) as 部门编码，人次
from test unpivot(人次 for deptno in(deptno_10_cnt,
deptno_20_cnt,
deptno_30_cnt))
--如果要把人次和工资同时转换，得用连接
select a.列名, a.部门编码, a.人次, b.工资
from (select substr(deptno, 1, 9) as 列名, substr(deptno, -6, 2) as 部门编码，人次
from test unpivot include nulls(人次 for deptno in(deptno_10_cnt,
deptno_20_cnt,
deptno_30_cnt))) a

inner join (select substr(deptno, 1, 9) as 列名，工资
from test unpivot include nulls(工资 for deptno in(deptno_10_sal,
deptno_20_sal,
deptno_30_sal))) b
on (a.列名 = b.列名)
--不用join 还是用unpivot
select deptno as 部门编码, 工资, 人次
from test unpivot include nulls(人次 for deptno in(deptno_10_cnt as 10,
deptno_20_cnt as 20,
deptno_30_cnt as 30)) unpivot include nulls(工资 for deptno2 in(deptno_10_sal as 10,
deptno_20_sal as 20,
deptno_30_sal as 30))
where deptno = deptno2

--抑制结果集中的重复值
select case
when lag(e.job) over(order by job, ename) = job then
null
else
job
end as 职位, ename as 姓名
from emp e
where e.deptno = 20
order by e.job, e.ename