Question

Trying to pivot dynamic data using LINQ or LAMBDA in C#/MVC4 and have pretty much come to the conclusion that its very difficult to do..

This is basically what I want to do:

I have been able to get this to work with known column names using this example: http://geekswithblogs.net/malisancube/archive/2009/04/21/using-lambda-or-linq-for-pivot-tables.aspx

But I cant find any examples for doing this with dynamic columns.

By dynamic columns I mean that there could be a new row with a different Name and FieldType that has not been in the table before at any time that also needs to be turned into a column.. any pointers?.

Answer 1

I don’t know LINQ so I will give you a version that can be used in a SQL Server stored procedure. This type of data transformation is known as a PIVOT. Since you are using SQL Server 2008+, you can use the function.

If you know the values that you want to transform, then you can hard-code the values:

SELECT nodeid, rowid,[FirstName], [LastName], [Title]
FROM
(
    SELECT nodeid, rowid, name, value
    FROM yourTable
) x
PIVOT
(
   max(value)
   for name in ([FirstName], [LastName], [Title])
)p

See SQL Fiddle with Demo

Then if you have an unknown number of values, you can implement dynamic SQL:

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(name) 
                    from yourtable
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT nodeid, rowid,' + @cols + ' from 
             (
                SELECT nodeid, rowid, name, value
                FROM yourTable
            ) x
            pivot 
            (
                max(value)
                for name in (' + @cols + ')
            ) p '

execute(@query)

See SQL Fiddle with Demo

Both return the results:

| NODEID | ROWID | FIRSTNAME | LASTNAME |  TITLE |
--------------------------------------------------
|      1 |     1 |    Alfred |   Beagle | (null) |
|      1 |     2 |    Freddy |   (null) | (null) |
|      1 |     3 |    (null) |     Grey |   Sir. |