使用TSQL

Question

给出一个包含有下列数据的表创建从平面数据分层数据？

ID ParentID Level Letter Country   City 
--------------------------------------------------------- 
1 NULL  0  A  NULL   NULL 
2 1   1  NULL Afghanistan  NULL 
3 2   2  NULL NULL   Kabul 
4 2   2  NULL NULL   Kandahar 
6 1   1  NULL Australia  NULL 
7 6   2  NULL NULL   Canberra 
8 6   2  NULL NULL   Sydney 
9 NULL  0  B  NULL   NULL 
10 9   1  NULL Belgium   NULL 
11 10   2  NULL NULL   Antwerp 
12 10   2  NULL NULL   Bruges 
13 10   2  NULL NULL   Brussels 

Answer 1

Declare @YourTable table (Country varchar(50), City varchar(50)) 
Insert Into @YourTable values 
('Afghanistan','Kabul'), 
('Afghanistan','Kandahar'), 
('Australia' ,'Canberra'), 
('Australia' ,'Sydney'), 
('Belgium' ,'Antwerp'), 
('Belgium' ,'Bruges'), 
('Belgium' ,'Brussels') 

; with cte0 as (
       Select Lvl0 = cast(Left(Country,1) as varchar(50)) 
         ,Lvl1 = cast(Country as varchar(50)) 
         ,Lvl2 = cast(City as varchar(50)) 
         ,ID0 = Dense_Rank() over (Order By Left(Country,1)) 
         ,ID1 = Dense_Rank() over (Order By Country) + 100 
         ,ID2 = Dense_Rank() over (Order By City) + 10000 
       From @YourTable 
       ) 
Select Distinct ID=ID0,ParentID=null,Level=0,Letter=Lvl0,Country=null,City=null,Path=concat('',Lvl0) from cte0 
Union All 
Select Distinct ID=ID1,ParentID=ID0,Level=1,Letter=null,Country=Lvl1,City=null,Path=concat('',Lvl0,' > ',Lvl1) from cte0 
Union All 
Select Distinct ID=ID2,ParentID=ID1,Level=2,Letter=null,Country=null,City=Lvl2,Path=concat('',Lvl0,' > ',Lvl1,' > ',Lvl2) from cte0 
Order By Path 

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