What is the difference between these two LINQ queries?

Question

Looking at the profiler, I see a few differences. The second query, which uses include , actually returns data from the associated CountryCodes secondary table. This part makes sense to me. However, I do not understand why this request has two joins. First, it performs a regular internal join between CountryCodes and CountyCodeTypes (by foreign key), which, I think, will be sufficient to return everything that is required to include . However, then it performs another outer join. Why?

var query = from codes in base.context.CountryCodes
            join codeTypes in base.context.CountryCodeTypes
            on codes.CountryCodeTypeId equals codeTypes.CountryCodeTypeId
            where codeTypes.CountryCodeTypeName == countryCodeType
            select codes;

var query = from codes in base.context.CountryCodes.Include("CountryCodeType")
            where codes.CountryCodeType.CountryCodeTypeName == countryCodeType
            select codes;

resulting sql:

 FROM   [dbo].[CountryCode] AS [Extent1]
 INNER JOIN [dbo].[CountryCodeType] AS [Extent2] ON [Extent1].[CountryCodeTypeId] = [Extent2].[CountryCodeTypeId]
 LEFT OUTER JOIN [dbo].[CountryCodeType] AS [Extent3] ON [Extent1].[CountryCodeTypeId] = [Extent3].[CountryCodeTypeId]
 WHERE [Extent2].[CountryCodeTypeName] = @p__linq__0

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Answer 1

SQL- Entity Framework.

INNER JOIN - where.

where codes.CountryCodeType.CountryCodeTypeName == countryCodeType

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var query = from codes in base.context.CountryCodes
            where codes.CountryCodeType.CountryCodeTypeName == countryCodeType
            select codes;

Answer 2

codes.CountryCodeType.CountryCodeTypeName == countryCodeType, CountryCodeType.

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