Question

以下查询1可以写为查询2吗？如果是，他们的工作方式不同。如果没有，那么我需要查询2的LINQ版本。

查询1：

select c.Name as 'Country', s.Name as 'State', city.Name as 'City' 
from CountryRegion c,CountryRegion s,CountryRegion city 
where  city.Id=11 and s.Id=city.CountryRegionParentId and c.Id=s.CountryRegionParentId

查询2：

select c.Name as 'Country', s.Name as 'State', city.Name as 'City' 
from CountryRegion as c inner join CountryRegion as s on c.Id=s.Id
inner join CountryRegion as city on s.Id=c.Id
where  city.Id=11 and s.Id=city.CountryRegionParentId and c.Id=s.CountryRegionParentId

Answer 1

在查询2中似乎存在错误，因为您使用的是不同的连接条件，而不是where子句中的条件（这没有用）。如果您将查询2重写为以下内容，则它应完全等同于查询1：

select c.Name as 'Country', s.Name as 'State', city.Name as 'City' 
from 
    CountryRegion as city inner join 
    CountryRegion as s on s.Id = city.CountryRegionParentId inner join
    CountryRegion as c on c.Id = s.CountryRegionParentId
where  city.Id=11

SQL - 2个不同写入的相等查询的工作方式不同

1 个答案: