innere Abfrage Ausgabe

Question

ich einen Zweifel an einer inneren Abfrage

Schema haben:

• DEPARTMENT (DEPTNUM, descrip, InstName, deptname, Bundesland, Postleitzahl)
• ACADEMIC (acnum , deptnum *, famname, givename, Initialen, Titel)
• PAPER (panum, Titel)
• AUTHOR (Panum, acnum **)
• FIELD (FeldNum, id, title)
• INTEREST (FeldNum, acnum **, descrip)

Ich habe die Ausgabe in diesem Format:

select 
    acnum, title, givename, famname 
from 
    academic a 
where 
    a.acnum in (select count(*) as no_of_papers, acnum 
       from author auth 
       join paper p on auth.panum = p.panum 
       group by acnum 
       having count(*) < 20) 
union 
select 
    acnum, title, givename, famname 
from 
    academic a 
where 
    a.acnum not in (select count(*) as no_of_papers, acnum 
        from author auth 
        join paper p on auth.panum = p.panum 
        group by acnum); 

Mit den Feldern in der SELECT-Anweisung der äußeren Abfragen möchte ich aber auch die count(*) als no_of_papers in der Ergebnismenge.

Ich habe mir schon seit einiger Zeit den Kopf gebrochen.

Answer 1

Verwenden Join

versuchen, wie diese

SELECT acnum,title,givename,famname,no_of_papers 
FROM academic a JOIN 
( 
    SELECT COUNT(*) AS no_of_papers,acnum 
    FROM author auth JOIN paper p ON auth.panum=p.panum 
    GROUP BY acnum HAVING COUNT(*)<20 

)x ON 1 = 1 
WHERE a.acnum IN (x.acnum) 

UNION 

SELECT acnum,title,givename,famname,no_of_papers 
FROM academic a 
(
    SELECT COUNT(*) AS no_of_papers,acnum 
    FROM author auth JOIN paper p ON auth.panum=p.panum 
    GROUP BY acnum 

)y ON 1=1 
WHERE a.acnum NOT IN (y.acnum) 

Answer 2

Ich glaube nicht, müssen Sie eine Vereinigung:

select 
    a.acnum, 
    MIN(a.title), -- only 1 value anyways if acnum is a primary key 
    MIN(a.givename), 
    MIN(a.famname), 
    count(p.panum) as no_of_papers 
from academic a 
left join author auth on a.acnum = auth.acnum 
left join paper p on auth.panum = p.panum 
group by a.acnum 
having 1 = 1 -- ??? no_of_papers < 20 ??? 
;