Solution Guide for Migrating Oracle on UNIX to SQL Server - Willy .Net

274 Developing: Applications — <strong>Migrating</strong> <strong>Oracle</strong> Pro*Ccn = SqlConnection(strConn)' open connectionscn.Open()' close connectionscn.Close()For more details on SqlConnection, refer tohttp://msdn.microsoft.com/library/default.asp?url=/library/enus/cpref/html/frlrfsystemdatasqlclientsqlconnectionclasstopic.asp3. Rewrite the queries and cursor functions.Pro*C uses embedded SQL to store the output of a query statement in a cursorfrom which rows can be fetched. Visual Basic.NET does not support cursors;instead, it uses several other methods <strong>for</strong> retrieving data sets from SQL queries.One of these data retrieval methods is the DataReader object, which is aligh tweight object that is read-only and, hence, ideal <strong>for</strong> queries. The following linkprovides access to more in<strong>for</strong>mation on retrieving data using DataReader object:http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpcontheadonetdatareader.asp.● Here are some common cursor operations encountered in Pro*C applications:Defining a cursor:●EXEC SQL DECLARE cust_cursor FORSELECT CustomerID, CompanyName FROM Customers;Opening the cursor:EXEC SQL OPEN cust_cursor;Fetching rows using the cursor:<strong>for</strong> (;;){EXEC SQL WHENEVER NOT FOUND DO break;EXEC SQL FETCH cust_cursor INTO :customerid, :companyname;printf("CustomerID: %s – CompanyName: %s\n", customerid,companyname);}Closing the cursor:EXEC SQL CLOSE cust_cursor;Although SQL Server does not support cursors, equivalent functions can becreated using ADO.NET:Defining the query:strSQL = "SELECT CustomerID, CompanyName FROM Customers"Creating a command object:Dim cmd As New SqlCommand(strSQL, cn)Creating a data reader object:Dim rdr As SqlDataReader = cmd.ExecuteReader()Displaying the data reader result set:While rdr.Read()Console.WriteLine(rdr("CustomerID") & " – " & rdr("CompanyName"))End WhileDo While rdr.Read()Console.WriteLine(rdr.GetInt32(0) & " " & _“ rdr.GetString(1) & " " & rdr.GetFloat(2))