Is linq's let keyword better than its into keyword?

Question

I\'m currently brushing up on LINQ and am trying to comprehend the difference between the let and using the into keyword. So far the let

Answer 1

Wanting to know the difference on DB side, wrote 2 Entity Framework queries.

• Let

  from u in Users
  let noVowel = u.FirstName.Replace("a","").Replace("e","").Replace("i","")
  where noVowel.Length >5
  select new {u.FirstName, noVowel}
  

• Into

  from u in Users
  select u.FirstName.Replace("a","").Replace("e","").Replace("i","")
  into noVowel
  where noVowel.Length >5
  select noVowel
  

The generated SQLs are almost identical. The SQL is not perfect, same string process code are repeated on 2 places (where and select).

SELECT 1 AS [C1], [Extent1].[FirstName] AS [FirstName], 
REPLACE(REPLACE(REPLACE([Extent1].[FirstName], N'a', N''), N'e', N''), N'i', N'') AS [C2]
FROM [dbo].[User] AS [Extent1]
WHERE ( CAST(LEN(REPLACE(REPLACE(REPLACE([Extent1].[FirstName], N'a', N''), N'e', N''), N'i', N'')) AS int)) > 5
GO

SELECT 
REPLACE(REPLACE(REPLACE([Extent1].[FirstName], N'a', N''), N'e', N''), N'i', N'') AS [C1]
FROM [dbo].[User] AS [Extent1]
WHERE ( CAST(LEN(REPLACE(REPLACE(REPLACE([Extent1].[FirstName], N'a', N''), N'e', N''), N'i', N'')) AS int)) > 5

Here is the SQL generated by LINQ-to-SQL

-- Region Parameters
DECLARE @p0 NVarChar(1000) = 'a'
DECLARE @p1 NVarChar(1000) = ''
DECLARE @p2 NVarChar(1000) = 'e'
DECLARE @p3 NVarChar(1000) = ''
DECLARE @p4 NVarChar(1000) = 'i'
DECLARE @p5 NVarChar(1000) = ''
DECLARE @p6 Int = 5
-- EndRegion
SELECT [t1].[FirstName], [t1].[value] AS [noVowel]
FROM (
    SELECT [t0].[FirstName], REPLACE(REPLACE(REPLACE([t0].[FirstName], @p0, @p1), @p2, @p3), @p4, @p5) AS [value]
    FROM [User] AS [t0]
    ) AS [t1]
WHERE LEN([t1].[value]) > @p6
GO

-- Region Parameters
DECLARE @p0 NVarChar(1000) = 'a'
DECLARE @p1 NVarChar(1000) = ''
DECLARE @p2 NVarChar(1000) = 'e'
DECLARE @p3 NVarChar(1000) = ''
DECLARE @p4 NVarChar(1000) = 'i'
DECLARE @p5 NVarChar(1000) = ''
DECLARE @p6 Int = 5
-- EndRegion
SELECT [t1].[value]
FROM (
    SELECT REPLACE(REPLACE(REPLACE([t0].[FirstName], @p0, @p1), @p2, @p3), @p4, @p5) AS [value]
    FROM [User] AS [t0]
    ) AS [t1]
WHERE LEN([t1].[value]) > @p6

Seems Linq-to-SQL is smarter than Entity Framework, string process performed only once.