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What is the best approach to run two querries on one Connection object (ODBC)?

Posted on 2004-09-07
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Last Modified: 2010-04-15
I have to work with the ODBC objects, running against a Cache 4.?? database.

I have successfully created an OdbcConnection object, OdbcCommand object, and an OdbcDataReader object (named drBorr) and have looped thru the whole result of the query with a "while (drBorr.Read())" loop, writing some of the data to a flat output file.

Now that the above "test" is done, what I want to do is run another query for each drBorr record against another table on the same database.  I could have written a larger query with a Join on the querried tables but I thought this approach was cleaner:
while (drBorr.Read())
{
  //Process this borrower record, writing appropriate values to the output flat file.
 
  ...create another OdbcConnection object?
  ...create another OdbcCommand object?
  ...create the drLoan OdbcDataReader object, but how exactly?
  while (drLoan.Read())
  {
    //Process this loan record, writing appropriate values to the output flat file.
  }
}

Please comment on the lines beginning with ... within the code.  The "borrower" query results in about 200,000 records with around 15 fields.  I presume this is not too large for a DataSet object, but I do not currently know how to create the DataSet object.

If you honestly think the large query is a better approach then I can go that route.  I just wanted to avoid the whole "does this loan belong to the same borrower as the previous loan...blah blah blah" which the separate querries via the while loops inherently do in a much cleaner fashion.

Thanks!
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Question by:KingDumbNo
2 Comments
 
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bowser17 earned 500 total points
ID: 12000453
I think rather than doing 200,000 queries you need to do an join, or your performance will be garbage.  If you are read only and forward, then you dont need a dataset.
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by:KingDumbNo
ID: 12020970
I figured one large chunk (with built in buffering and such) was better than 200,000 queries but I wanted to be sure.  C# has made reading a "recordset" much easier in that DataReaderVariable.Read() will just keep returning false at the end.  This made my prevSSN != currSSN logic much easier.  Here's a small code snippet, if anyone cares:

while (dr.Read())
{
    if (prevSSN != dr["BRACCT"].ToString())
        //do something with this new SSN

    //continue writing loan records for the same SSN
}
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