sql - 嵌套 SQL 计数

Question

我有两张表，成员和国家，我想做的是找到所有没有成员的国家。我有点迷路，这是我最好的猜测，但它不起作用：

SELECT CountryID
FROM Country 
WHERE (SELECT COUNT(MemberID) FROM Member WHERE PrCountryID = CountryID) = 0

任何帮助将不胜感激。

新杰克

Answer 1

select countryID from Country C left join member M on C.CountryID=M.CountryID where M.MemberID is null

Answer 2

尝试使用not exists子句：

SELECT C.CountryID
FROM Country C
WHERE not exists(SELECT 1 FROM Member M WHERE M.PrCountryID = C.CountryID) 

Answer 3

在没有看到表格的情况下，我认为您需要这样的东西

select * from Country c
left outer join Member m on m.PrCountryID = c.CountryID
where m.PrCountryID is null