国家和城市的国家明智数据

Question

我有这些表：

预期输出：

Answer 1

使用简单的联接即可实现：

select s.name,c.name,ci.name from @state s
join @Country c
on s.countryid = c.id
join @city Ci on ci.stateid=s.ID

Answer 2

简单的左联接将为您工作：

SELECT 
    S.Name AS State, 
    C.Name AS Country,
    CT.Name AS City
FROM 
    State S 
LEFT JOIN Country C 
    ON C.Id = S.Country_Id 
LEFT JOIN City CT
    ON CT.StateId = S.Id 

Answer 3

使用join可以实现它。

select ,b.name a.name,c.name Country as a inner join State as b on a.id=b.CountryID inner join City as c on c.StateId=b.id