Oracle查询返回一个基于列的行值

Question

我目前有在WHERE子句中的应用选择多行数据的查询：

SELECT 
    APP_NAME, 
    NAME, 
    ROLE 
FROM APP_PERSON 
WHERE APP_NAME='ABCD' 
ORDER BY APP_NAME,NAME 

这将返回：

ABCD Bob Executive Director 
ABCD Kim Director 
ABCD Sara Associate Director 
ABCD Tim VP 

我'这样做是为了返回一行，与最低的标题'角色'的人。顺序是：副总监，董事，执行董事，副总裁（这是唯一的选择）。

因此，对于上面的例子，我想返回的唯一行：

ABCD Sara Associate Director 

如果不是一个副主任，我想导演。我如何创建一个能够做到这一点的查询。我假设某种DECODE，但不知道该去哪里。谢谢你的帮助！

Answer 1

有多种方法可以解决这个问题。我宁愿在优先明确加入，然后用row_number()选择您想要的行：

select app_name, name, role 
from (SELECT APP_NAME, NAME, ROLE, 
      ROW_NUMBER() over (partition by app_name order by priority) as seqnum 
     FROM APP_PERSON p join 
      (select 'Associate Director' as role, 1 as priority from dual union all 
      select 'Director', 2 from dual union all 
      select 'Executive Director', 3 from dual union all 
      select 'VP', 4 from dual 
      ) r 
      on p.role = r.role 
    ) t 
WHERE APP_NAME='ABCD' and seqnum = 1 
ORDER BY APP_NAME, NAME 

Answer 2

顺序云：副总监，总监，执行董事，副总裁（这是唯一的选项）

我希望下面的查询将为您提供答案。

SELECT 
    APP_NAME, 
    NAME, 
    ROLE 
FROM APP_PERSON 
WHERE APP_NAME='ABCD' 
ORDER BY APP_NAME,NAME 
where rownum = 1 
order by ROLE 

Answer 3

如何使用公共表expresion像这样：

WITH cte AS (
    SELECT 
    app_name 
    ,name 
    ,role 
    ,MIN(CASE role 
      WHEN 'Associate Director' THEN 1 
      WHEN 'Director' THEN 2 
      WHEN 'Executive Director' THEN 3 
      WHEN 'VP' THEN 4) AS role_level 
    FROM app_person 
    WHERE app_name='ABCD' 
) 
SELECT 
    r.* 
FROM cte r 
    INNER JOIN (
    SELECT 
     name 
     ,MIN(role_level) AS role_level 
    FROM cte rl 
    GROUP BY name) ON r.name = rl.name AND r.role_level = rl.role_level 
ORDER BY 
    r.app_name 
    ,r.name