sql - 如何在sql中旋转第二列

Question

这是我当前的数据集:

rname   ename
Advises Grad_student
Advises Faculty
Chairs  Department
Chairs  Faculty

我正在尝试将其转换为这种格式:

rname    ename1        ename2
advises  grad_student  faculty
chairs   department    faculty

这是我迄今为止尝试过的:

select distinct 
r1.rname, r1.ENAME as ename1,r2.ENAME as ename2
from [dbo].[RELATIONSHIPS] r1
inner join(
select distinct 
RNAME, ENAME

from [dbo].[RELATIONSHIPS]) r2
on r1.RNAME = r2.RNAME
where r1.ENAME <> r2.ENAME

order by r1.rname

这是我得到的回复:

rname   ename1        ename2
Advises Grad_student  Faculty
Advises Faculty       Grad_student
Chairs  Department    Faculty
Chairs  Faculty       Department

我该如何修复我的代码才能只返回 1 行？

Answer 1

您可以将row_number()与条件聚合结合使用:

with cte as  (
  select rname, ename, row_number() over (partition by rname order by ename) rn
  from relationships
  )
select rname, 
  max(case when rn = 1 then ename end) ename1,
  max(case when rn = 2 then ename end) ename2
from cte
group by rname

• SQL Fiddle Demo