SQL“case when”查询

Question

我的学校项目需要这个我无法创建的查询。

该表包含4列：

document id，party_id，full name，party role。

对于doc_id我有2行，grantor 1为grantee。 我想做单排，但我没有成功的情况下。 请帮忙。

SELECT document_id, 
       case  when party_role ='grantor' then full_name 
       case  when party_role ='grantee' then full_name  
from sales.all_sales

Answer 1

SELECT document_id,
       CASE(party_role)
           WHEN 'grantor'
           THEN full_name
           WHEN 'grantee'
           THEN full_name
           ELSE ''
       END
FROM sales.all_sales

Answer 2

SELECT DISTINCT document_id, 
   case  when party_role ='grantor' then full_name end Grantor,
   case  when party_role ='grantee' then full_name  end Grantee

from sales.all_sales

如果你想聚合字段，请尝试：

SELECT DOCUMENT_ID,
LISTAGG(GRANTOR,',') WITHIN GROUP (ORDER BY GRANTOR) GRANTOR,
LISTAGG(GRANTEE,',') WITHIN GROUP (ORDER BY GRANTEE) GRANTEE
FROM (
 SELECT DISTINCT document_id, 
   case  when party_role ='grantor' then full_name end Grantor,
   case  when party_role ='grantee' then full_name  end Grantee

from sales.all_sales
)
GROUP BY DOCUMENT_ID

Answer 3

您想要聚合。您希望每个document_id有一个结果行，因此按其分组。您希望每个都构建一系列授权者和受赠者。请使用LISTAGG。

select
  document_id, 
  listagg(case when party_role = 'grantor' then full_name end, ',')
          within group (order by full_name) as grantor,
  listagg(case when party_role = 'grantee' then full_name end, ',')
          within group (order by full_name) as grantee
from sales.all_sales
group by document_id;

Answer 4

在Oracle 11g中，您可以使用pivot和listagg作为聚合函数来执行此操作：

select * from t
 pivot (listagg(name, ', ') within group (order by name) 
        for role in ('grantor' grantors, 'grantee' grantees))

^演示：

with t(id, name, role) as (
    select 2, 'James',    'grantor' from dual union all
    select 2, 'Tom',      'grantor' from dual union all
    select 2, 'Victoria', 'grantee' from dual union all
    select 2, 'Anty',     'grantee' from dual )
select * from t
 pivot (listagg(name, ', ') within group (order by name) 
                            for role in ('grantor' grantors, 'grantee' grantees))

^结果：

        ID  GRANTORS         GRANTEES
----------  ---------------  -----------------
         2  James, Tom       Anty, Victoria