行转列、列转行题目(收集中...)

一、列转行

1、把如下表

year  month amount
1991   1     1.1
1991   2     1.2
1991   3     1.3
1991   4     1.4
1992   1     2.1
1992   2     2.2
1992   3     2.3
1992   4     2.4
转换为结果表
year m1  m2  m3  m4
1991 1.1 1.2 1.3 1.4
1992 2.1 2.2 2.3 2.4

方法(MAX+DECODE+GROUP BY)：

with t as 
(
select 1991 as year, 1 as month,1.1 as amount from dual
union all
select 1991 as year, 2 as month,1.2 as amount from dual
union all
select 1991 as year, 3 as month,1.3 as amount from dual
union all
select 1991 as year, 4 as month,1.4 as amount from dual
union all
select 1992 as year, 1 as month,2.1 as amount from dual
union all
select 1992 as year, 2 as month,2.2 as amount from dual
union all
select 1992 as year, 3 as month,2.3 as amount from dual
union all
select 1992 as year, 4 as month,2.4 as amount from dual
)
select year, MAX(decode(month,1,amount,null)) m1,
MAX(decode(month,2,amount,null)) m2,
MAX(decode(month,3,amount,null)) m3,
MAX(decode(month,4,amount,null)) m4
from t
)
group by year

 二、多行转一行

select listagg(ename,',')
within group(order by empno desc)
from emp;