Question

Table like

datetime          a1   b1   x2 ...  
07-01-2009 13:10   8    9    10  
07-01-2009 13:11   8    8    2  
07-01-2009 13:12   9    1    1    

1 row per second for a whole day (=86400 rows); ~40 columns; all same format
I’m looking for a way to retrieve a max value and the time for a column to specify.

I’m looking for a way to retrive a max value and the according time for a column to specify within a timeframe.

Something like

Select top 1 time,a1 from table
    where (datetime>=begin and datetime<end) 
    order by a1 desc   

will work but I cannot use the column as a parameter.

A LINQ solution or a SP would be great.

Do I have to worry about performance when sorting a whole dataset to retrieve a max value? Maybe MAX function will be faster.

UPDATE

I tried to implement it the dynamic linq way, like Timothy (tvanfossen) suggested

Dim q2 = context.table _
  .Where("t >= @0 AND t < @1", begin, end) _
  .OrderBy("@0 desc", col) _
  .Take(1) _
  .Select(col)

BUT this returns the first value in the table.
This returns the first value in the time frame and not the max value. Looking at the SQL profiler I see that there is no ORDER clause.
Any idea?

UPDATE 2
For some reason the substitution value does not work in the orderby clause.
.OrderBY (col + ” desc”) works

Answer 1

If you want the column name to be dynamic, you might want to use Dynamic Linq from the VS2008 code samples. Then you can specify the name of the column to sort by.

var query = context.table
                   .Where( t = t.begin <= date && date < t.end )
                   .OrderBy( "a1 desc" )
                   .Take(1)
                   .SingleOrDefault();