sqlite 树型结构查询

表结构：tblCity(ID, ParentID, Name)

因为sqlite 没有row_number函数，也不能递归查询，所幸它有RowID 这个字段。只好采用这种 笨方法

1）

select ID,Name,1 as Level from tblCity where ParentID=0
union all 
select a.ID,a.Name,c.RowID as Level from tblCity a 
inner join tblCity b on a.ParentID=b.ID
inner join 
(
      select ParentID from tblCity group by ParentID
) c on a.ParentID=c.ParentID

2）

select ID,Name,1 as Level from tblCity where ParentID=0
union all 
select a.ID,a.Name,c.RowID as Level from tblCity a 
inner join tblCity b on a.ParentID=b.ID
inner join 
(
      select ParentID from tblCity group by ParentID
) c on a.ParentID=c.ParentID