Oracle查詢返回一個基於列的行值

Question

我目前有在WHERE子句中的應用選擇多行數據的查詢：

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

這將返回：

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

我'這樣做是爲了返回一行，與最低的標題'角色'的人。順序是：副總監，董事，執行董事，副總裁（這是唯一的選擇）。

因此，對於上面的例子，我想返回的唯一行：

ABCD Sara Associate Director 

如果不是一個副主任，我想導演。我如何創建一個能夠做到這一點的查詢。我假設某種DECODE，但不知道該去哪裏。謝謝你的幫助！

Answer 1

有多種方法可以解決這個問題。我寧願在優先明確加入，然後用row_number()選擇您想要的行：

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

順序雲：副總監，總監，執行董事，副總裁（這是唯一的選項）

我希望下面的查詢將爲您提供答案。

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像這樣：

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