SQL解析来自同一表的外键

Question

I was hoping you could help a beginner with something. I got a query that references several tables. Two of the tables I'm referencing hold a foreign key, which would be a different records in a joint table.

Example here would be orgunit.shortname. This filed would be called twice, but in different relations.

I'm sure that there is a way to do this without using a temp table, but I kept failing with several attempts.

Any help would really be appreciated.

Best Dennis

The current query is below.

select 
    orgunit.shortname       AS OnsiteDept, 
    department.shortname    AS DeptName, 
    OrgUnitParent.orgunitid AS ParentID,
    Orgunit.xrefcode        AS OrgXref,
    Orgunit.departmentid    AS DeptID,  
    Orgunit.shortname       AS Parentshotname,
    Orgunit.orglevelid      AS OrgLevel

        from orgunit
        left join   department
        on orgunit.departmentid = department.departmentid

        left join   OrgUnitParent
        on orgunit.orgunitid = OrgUnitParent.orgunitid
        AND OrgUnitParent.orgunitid = orgunit.orgunitid

            where orgunit.shortname

Answer 1

select ou.shortname       AS OnsiteDept, 
       d.shortname    AS DeptName, 
       oup.orgunitid AS ParentID,
       ou.xrefcode        AS OrgXref,
       ou.departmentid    AS DeptID,  
       oup.shortname       AS Parentshotname,
       ou.orglevelid      AS OrgLevel    
from orgunit ou left join
     department d
     on ou.departmentid = d.departmentid left join
     OrgUnitParent
     on oup.orgunitid = ou.parent_orgunitid left join
     orgunit oupp
     on oupp.orgunitid = oup.orgunitid
where ou.shortname;

The join between an org unit and its parent is not obvious. Perhaps there is some sort of parent id.