title: Select only a single column in LINQ
body: <p>The EntityModel is defined as:
  <em>Personnel has a link to a Country</em></p>
  
  <p>When executing this code in LinqPad, I see that the SQL which is generated is not optimized (all fields are returned) in the first query ? What am I missing here or doing wrong ?</p>
  
  <p><strong>Query 1 LINQ</strong></p>
  
  <pre><code>var Country = Countries.FirstOrDefault(o =&gt; o.Id == 100000581);
  var personnelIds = Country.Personnels.Select(p =&gt; p.Id).ToArray();
  personnelIds.Dump();
  </code></pre>
  
  <p><strong>Query 1 SQL</strong></p>
  
  <pre><code>exec sp_executesql N'SELECT [t0].[Id], [t0].[Version], [t0].[Identifier], [t0].[Name], , [t0].[UpdatedBy] FROM [Personnel] AS [t0] WHERE [t0].[Country_Id] = @p0',N'@p0 bigint',@p0=100000581
  </code></pre>
  
  <p><br>
  <br></p>
  
  <p><strong>Query 2 LINQ</strong></p>
  
  <pre><code>var Country = Countries.FirstOrDefault(o =&gt; o.Id == 100000581);
  var personnelIds2 = Personnels.Where(p =&gt; p.Country == Country).Select(p =&gt; p.Id).ToArray();
  personnelIds2.Dump();
  </code></pre>
  
  <p><strong>Query 2 SQL</strong></p>
  
  <pre><code>exec sp_executesql N'SELECT [t0].[Id] FROM [Personnel] AS [t0] WHERE [t0].[Country_Id] = @p0',N'@p0 bigint',@p0=100000581
  </code></pre>
  
  <p><br>
  The database used is SQL Express 2008. And LinqPad version is 4.43.06</p>