如何在SQL中转换输出表的单列？

Question

我是编码的新手，并不理解Pivot函数只是想知道是否有人可以帮助我以下查询。

我在下面有一个SQL查询

select distinct hapf.position_code, pg.name
from
hr_all_positions_f hapf, PER_VALID_GRADES_F pvgf, per_grades pg
where
hapf.position_id = pvgf.position_id
and pvgf.grade_id = pg.grade_id
and hapf.position_code = 'ABCD'

这给出了如下输出

POSITION_CODE    NAME
ABCD             Grade03
ABCD             Grade04
ABCD             Grade05

但我想要输出如下

POSITION_CODE    Grade1    Grade2    Grade3
ABCD             Grade03   Grade04   Grade05

有人可以帮助我完成我需要在我的SQL查询中进行的更改，如果我有另一个列的值，我想要进行Pivot会发生什么？

谢谢，

Shivam

Answer 1

你可能需要：

-- test case
with yourQuery (POSITION_CODE, NAME) as (
    select 'ABCD', 'Grade01' from dual union all
    select 'ABCD', 'Grade02' from dual union all
    select 'ABCD', 'Grade03' from dual
)
-- query
select *
from yourQuery
pivot ( max (Name) for name in
        (
            'Grade01' as Grade1,
            'Grade02' as Grade2,
            'Grade03' as Grade3
         )
       )

这使：

POSITION_CODE GRADE1  GRADE2  GRADE3 
------------- ------- ------- -------
ABCD          Grade01 Grade02 Grade03

如果您需要处理更多列，则需要编辑代码，因为您需要事先知道结果集的列数和名称：

-- test case
with yourQuery (POSITION_CODE, NAME) as (
    select 'ABCD', 'Grade01' from dual union all
    select 'ABCD', 'Grade02' from dual union all
    select 'ABCD', 'Grade03' from dual union all
    select 'ABCD', 'Grade04' from dual
)
-- query
select *
from yourQuery
pivot ( max (Name) for name in
        (
            'Grade01' as Grade1,
            'Grade02' as Grade2,
            'Grade03' as Grade3,
            'Grade04' as Grade4
         )
       )

因此得到：

POSITION_CODE GRADE1  GRADE2  GRADE3  GRADE4 
------------- ------- ------- ------- -------
ABCD          Grade01 Grade02 Grade03 Grade04

Answer 2

SELECT POSITION_CODE, Grade03,Grade04,Grade05 FROM   
(SELECT POSITION_CODE, NAME, Value_TO_PIVOT FROM mytable)Tab1  
PIVOT  
(  
SUM(Value_TO_PIVOT) FOR NAME IN (Grade03,Grade04,Grade05)) AS Tab2  
ORDER BY Tab2.POSITION_CODE

您可以参考此link来编写动态查询，如果您不知道要转动的值或值更多，则需要该动态查询

Answer 3

我从命中和跟踪中解决了我的问题，下面是代码希望它能帮助别人。

    select position_code,
max(case when position_num = 1 and pg_num = 1 then grade_name end) as Grade1,
max(case when position_num = 1 and pg_num = 2 then grade_name end) as Grade2,
max(case when position_num = 1 and pg_num = 3 then grade_name end) as Grade3
from
(
select 
dense_rank() over (order by hapf.position_code) position_num,
dense_rank() over (partition by hapf.position_code order by pg.name) pg_num,
hapf.position_code, 
pg.name as grade_name
from
hr_all_positions_f hapf, PER_VALID_GRADES_F pvgf, per_grades pg
where
hapf.position_id = pvgf.position_id
and pvgf.grade_id = pg.grade_id
and hapf.position_code = 'ABCD'
) group by position_code

谢谢，

Shivam