Question

I have an SQL query like this:

set @fromdate = '2012/01/01 00:00:00'
set @todate = '2013/01/01 00:00:00'

SELECT TableOne.date_time, TableTwo.* 
FROM TableOne 
INNER JOIN TableTwo ON TableOne.gprs_id = TableTwo.recordid 
WHERE date_time >= @fromdate AND date_time <= @todate

I use it in .net 4 (c#) like this:

string strSQL = "SELECT TableOne.date_time, TableTwo.* FROM TableOne INNER JOIN TableTwo ON " +
                "TableOne.gprs_id = TableTwo.recordid where date_time >= @fromdate AND date_time <= @todate";

var pCommand = pConnectionWrapper.DBConnection.CreateCommand();
pCommand.CommandText = strSQL;

var paramFromDate = pCommand.CreateParameter();
paramFromDate.ParameterName = "@fromdate";
paramFromDate.DbType = DbType.DateTime;
paramFromDate.SourceColumn = "date_time";
paramFromDate.Value = fromDate;
pCommand.Parameters.Add(paramFromDate);

var paramToDate = pCommand.CreateParameter();
paramToDate.ParameterName = "@todate";
paramToDate.DbType = DbType.DateTime;
paramToDate.SourceColumn = "date_time";
paramToDate.Value = toDate;
pCommand.Parameters.Add(paramToDate);

var pReader = pCommand.ExecuteReader();

while (pReader.Read())
{
   var someValue = double.Parse(pReader["somevalue"].ToString());
   var date = DateTime.Parse(pReader["date_time"].ToString());

   var someObject = new someObject(someValue, someDate);
   someObjects.Add(comeObject);
}

Running this query is much faster in SQL Server Management Studio than from .net. Iterating through rows is extremely slow from .net. As I think this inner join causes this (?), because my other queries that does not contain joins are really fast under .net.

Can I improve the query performance from .net? Using datasets instead of reader or sg like this?

Thank you very much!

Answer 1

This will not really fix the query but will get the data from the query more efficiently.
Return only the columns you need by name. Reader should be faster than a dataset.

Double someValue;
DateTime date;
while (pReader.Read())
{
   someValue = pReader.GetDouble(0);
   date = pReader.GetDate(1);

   var someObject = new someObject(someValue, someDate);
   someObjects.Add(comeObject);
}

//or
while (pReader.Read())
{
   someObjects.Add(new someObject(pReader.GetDouble(0), pReader.GetDate(1)));
}

As for the query it seems pretty basic.

Comment out the 2 object lines to see if that is possibly the bottleneck.