比较oracle中的多行和多列

Question

我正在使用 Oracle SQL，假设我有一个这样的表，其中包含项目各个阶段的开始日期和完成日期。

Project No	STAGES	Start Date	completion date
PROJ_001	1	12-MAR-21	12-MAR-21
PROJ_001	2	14-MAR-21	14-MAR-21
PROJ_001	3	15-MAR-21	15-MAR-21
PROJ_001	4	18-MAR-21	18-MAR-21
PROJ_002	1	16-MAR-21	18-MAR-21
PROJ_002	2	17-MAR-21	19-MAR-21
PROJ_002	3	19-MAR-21	19-MAR-21
PROJ_002	4	21-MAR-21	23-MAR-21

我需要将输出如下表所示。 对于阶段级别的输出，需要比较完成日期和开始日期 对于项目级别，需要检查项目的最后阶段（即第 4 阶段）

Project No	STAGES	Start Date	completion date	Output 1	output 2 project level
PROJ_001	1	12-MAR-21	12-MAR-21	ON TIME	ON TIME
PROJ_001	2	14-MAR-21	14-MAR-21	ON TIME	ON TIME
PROJ_001	3	15-MAR-21	15-MAR-21	ON TIME	ON TIME
PROJ_001	4	18-MAR-21	18-MAR-21	ON TIME	ON TIME
PROJ_002	1	16-MAR-21	18-MAR-21	DELAYED	DELAYED
PROJ_002	2	17-MAR-21	19-MAR-21	DELAYED	DELAYED
PROJ_002	3	19-MAR-21	19-MAR-21	ON TIME	DELAYED
PROJ_002	4	21-MAR-21	23-MAR-21	DELAYED	DELAYED

谁能帮帮我？

Answer 1

您可以编写 2 个查询，{Q1} 返回“输出 1”所需的值，{2} 为您提供“输出 2”的值。一旦你看到这些查询产生了正确的结果，就将它们连接在一起。示例见DBfiddle。

查询 1（“阶段级别”）

select 
  projectno, stages, startdate, completiondate 
, case
    when startdate = completiondate then 'on time'
    else 'delayed'
  end output_1
from projects;

查询 2（“项目级别”）

-- look at the last stage (only).  CASE may need tweaking
select 
  projectno
, case 
    when max( startdate ) = max( completiondate ) then 'on time'
    else 'delayed'
  end output_2  
from projects
group by projectno
;

加入

select Q1.*, Q2.output_2
from (
  select 
    projectno, stages, startdate, completiondate 
  , case
      when startdate = completiondate then 'on time'
      else 'delayed'
    end output_1
  from projects
) Q1 join (
  select 
    projectno
  , case 
      when max( startdate ) = max( completiondate ) then 'on time'
      else 'delayed'
    end output_2  
  from projects
  group by projectno
) Q2 on Q1.projectno = Q2.projectno 
order by Q1.projectno, Q1.startdate
;

-- result
PROJECTNO   STAGES  STARTDATE   COMPLETIONDATE  OUTPUT_1  OUTPUT_2
PROJ_001    1      12-MAR-21    12-MAR-21       on time   on time
PROJ_001    2      14-MAR-21    14-MAR-21       on time   on time
PROJ_001    3      15-MAR-21    15-MAR-21       on time   on time
PROJ_001    4      18-MAR-21    18-MAR-21       on time   on time
PROJ_002    1      16-MAR-21    18-MAR-21       delayed   delayed
PROJ_002    2      17-MAR-21    19-MAR-21       delayed   delayed
PROJ_002    3      19-MAR-21    19-MAR-21       on time   delayed
PROJ_002    4      21-MAR-21    23-MAR-21       delayed   delayed

附录

（采纳@Thorsten Kettner 的建议：）您还可以使用 max() 以分析函数的形式，例如

-- remove the comments -> see the output of max(...) over (...)
select 
  projectno, stages, startdate, completiondate 
, case
    when startdate = completiondate then 'on time'
    else 'delayed'
  end output_1
, case 
    when 
      max( startdate ) over ( partition by projectno  )
    = max( completiondate )  over ( partition by projectno )
    then 'on time'
    else 'delayed'
  end output_2
-- , max( startdate ) over ( partition by projectno  ) maxstart_
-- , max( completiondate )  over ( partition by projectno ) maxcompletion_
from projects;

DBfiddle