SQL Server之连接

select a.[Name] as ‘地区名‘,
       b.[Name] as ‘上级地区名‘,
       c.[Name] as ‘上上级地区名‘
from tb_TestTreeView as a
left join tb_TestTreeView as b
     on a.Parent = b.ID 
left join tb_TestTreeView as c
     on b.parent=c.id

结果为：

自连接三级（内联接）：

select a.[Name] as ‘地区名‘,
       b.[Name] as ‘上级地区名‘,
       c.[Name] as ‘上上级地区名‘
from tb_TestTreeView as a
inner join tb_TestTreeView as b
     on a.Parent = b.ID 
inner join tb_TestTreeView as c
     on b.parent=c.id

结果为：

自连接四级（左链接）：

select a.[Name] as ‘地区名‘,
       b.[Name] as ‘上级地区名‘,
       c.[Name] as ‘上上级地区名‘,
       d.[Name] as ‘上上上级地区名‘
from tb_TestTreeView as a
left join tb_TestTreeView as b
     on a.Parent = b.ID 
left join tb_TestTreeView as c
     on b.parent=c.id
left join tb_TestTreeView as d
     on c.parent=d.id

结果为：

自连接四级（内链接）：

select a.[Name] as ‘地区名‘,
       b.[Name] as ‘上级地区名‘,
       c.[Name] as ‘上上级地区名‘,
       d.[Name] as ‘上上上级地区名‘
from tb_TestTreeView as a
inner join tb_TestTreeView as b
     on a.Parent = b.ID
inner join tb_TestTreeView as c
     on b.Parent = c.ID
inner join tb_TestTreeView as d
     on c.Parent = d.ID

结果为：

SQL Server之连接

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