Question

这是我当前的数据集：

rname   ename
Advises Grad_student
Advises Faculty
Chairs  Department
Chairs  Faculty

我正试图让它变成这种格式：

rname    ename1        ename2
advises  grad_student  faculty
chairs   department    faculty

这是我到目前为止所尝试的内容：

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

这是我要回来的：

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

我如何才能修复我的代码以便只返回1行？

Answer 1

您可以将row_number()与conditional aggregation：

一起使用

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

Answer 2

在oracle中

 select * from 
 (select rname,ename,
 RANK() over (partition by rname order by ename) Id
 FROM relationships)
 PIVOT(MAX(ename) for Id in (1 as ename1, 2 as ename2))

Answer 3

如果只有两个，那就这样做吧。简短又甜蜜。

rescue Stripe::CardError => e
  error = e.message
  Rails.logger.error "Stripe card error for account #{@account}, error #{e}"

如何在tsql中转动第二列

3 个答案: