这样试一试
select p.[Name], (select count(CityId) from [City] c where c.[ProvId] = p.[ProvId]) as n from [Prov] p order by (select count(CityId) from [City] c where c.[ProvId] = p.[ProvId]) asc
select p.[Name], (select count(CityId) from [City] c where c.[ProvId] = p.[ProvId]) as n from [Prov] p order by (select count(CityId) from [City] c where c.[ProvId] = p.[ProvId]) asc
(select p.[Name], (select count(CityId) from [City] c where c.[ProvId] = p.[ProvId]) as n from [Prov] p) t
order by t.n asc