SUM(order_size) group by market_id

or

SUM(order_size) where market_id = 19

I am not sure if the second statement is a valid one but I need something of this effect. Even groupby would work.

Now, How can I do this in

DataSet.DataTables[0].Select() ???

What kind of expression should I write in select method ??

I tried this

.Select("SUM(order_size) group by o.market_id ")

but got an exception

"An unhandled exception of type 'System.Data.SyntaxErrorException' occurred in system.data.dll

Additional information: Syntax error: Missing operand after 'group' operator."

What operand am I missisng here ??

Thanks,