也许重新格式化数据是有意义的,因为除了计算国家和地区之外,还有其他种类的查询。
CREATE TABLE #CountriesRegions
(
[ID] [int] NOT NULL,
parentid [int] NULL,
segment [nvarchar](50) NULL)
insert into #CountriesRegions values (1,null,'usa'), (2,1, 'california'), (3, null, 'canada'), (4, 3, 'quebec'), (5, 1, 'NY')
select * from #CountriesRegions
Create table #Country
([ID] [int] NOT NULL
,[country_name] [nvarchar](50) NOT NULL)
Insert into #Country select ID, segment AS country_name from #CountriesRegions where parentid IS NULL
select * from #Country
Create table #Region
([ID] [int] NOT NULL
,[country_id] [int] NOT NULL
,[region_name] [nvarchar](50) NOT NULL)
Insert into #Region select ID, parentid AS country_ID, segment AS region_name from #CountriesRegions where parentid IS NOT NULL
select * from #Region
Select COUNT(*) As 'Num of Countries' from #Country
Select COUNT(*) As 'Num of Regions' from #Region
表中有多少层嵌套? –
只是2:国家和地区 – DanSm