使用带比较的子查询 - Oracle

Question

我一直在尝试将结果操纵到这三个查询中，但我不知道我在做什么错了

列出所有参与少于三个小组的学术成员。

列出最大组数领先的学术ID

使用此查询（第一部分）

SELECT a.ID  , min(a.name) as Name  
FROM Academic a , researchGroup r 
WHERE count(r.managerID)>3
GROUP BY a.ID;

但是好像不行。

我有这个关系模式

researchGroup(name (P.R Key Composite) , codeD , mainResearchArea , managerID /* forgien key with AcademicStaff(ID) */ , labID (P.R Key Composite) )

AcademicStaff(ID {PR KEY} , name)

任何解决方案？

Answer 1

以下将为您提供学术人员名单和管理的研究小组数量：

SELECT
    *

FROM
    (
        SELECT 
            ac.ID                   AS academic_id
            ,MAX(ac.name)           AS academic_name
            ,COUNT(rg.managerID)    AS num_groups_managed
            ,DENSE_RANK() OVER (ORDER BY COUNT(rg.managerID) DESC) AS academic_rank

        FROM 
            Academic AS ac

        INNER JOIN
            researchGroup AS rg
            ON (rg.managerID = ac.ID)

        GROUP BY 
            ac.ID

    ) AS subquery

WHERE
    --** uncomment the following line for the academics managing above 3 groups
    --num_groups_managed >= 3

    --** or uncomment the following line for the top-ranked academics (there could be more than 1)
    --academic_rank = 1

ORDER BY
    academic_rank ASC
    ,academic_name ASC

取消注释 WHERE 子句的相关部分将为您提供所需的结果。

顺便说一句，自从我使用 Oracle SQL 以来已经有一段时间了，所以请原谅任何小的语法错误（特别是，我不记得 Oracle 是否接受 AS 之后的关键字 table姓名).

使用带比较的子查询 - Oracle

Using Sub-queries with comparison - Oracle

sql

subquery

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