用于自联接的SQL查询

Question

嗨，我有上表结构的成员表。在这里，我们可以通过列GroupID ..

轻松查询MemberID

示例...对于GroupID = 1，我们将得到结果

ObjectType    MemberID
-----------------------------
  user         1
  user         2
  group        2
  group        3

但是，我需要的是，我想列出嵌套成员（表示组成员的成员....对于group = 2，group = 3）

预期结果应该是这样的

ObjectType    MemberID
-----------------------------
  user         1
  user         2
  group        2
  group        3
  user         4
  group        3
  user         7

任何人都可以帮我写这个案例的查询吗？。

Answer 1

为什么需要JOIN？如果我没弄错的话，你正在处理1张桌子？

SELECT ObjectType, MemberID
From   Table
Group by GroupId, ObjectType, MemberID
Order by MemberID

Answer 2

实现此目的的一种方法是使用递归common table expression或CTE 像这样的东西

;with cte as 
(
    select *, groupid as mastergroup,1 as level from yourtable 
    union all       
    select t1.memberid, t1.objecttype, null, cte.mastergroup, level+1
    from cte 
        inner join yourtable t1
            on t1.groupid=cte.memberid
    where cte.objecttype='g'
) 
select * from cte
where mastergroup=1

但是，从您的表结构中，不清楚如何定义组的成员。

Answer 3

你可以在这里使用CTE

    ;WITH tableResult (ObjectType, ObjectType)
AS
(
-- Anchor member definition
SELECT TD.ObjectType, TD.ObjectType
FROM yourtableAS TD   
    UNION ALL
-- Recursive member definition
SELECT TD.ObjectType, TD.ObjectType
FROM TaskDependency AS TD
INNER JOIN tableResult AS TR
    on TD.groupid= TR.memberid 
        and TR.objecttype='group'
    )

--then select from this cte
Select * from tableResult