SQLConnect() - ODBC API - Oracle to SQL Server and SQL Azure Migration

SQLConnect function establishes the connection to a database using an existing ODBC data source, user name and password.

Quick Example: 

   // Connect to Oracle
   SQLRETURN retcode = SQLConnect(hdbc, "oracle_dsn", SQL_NTS, "scott", SQL_NTS, "tiger", SQL_NTS);

Overview

Conversion issues:

Oracle SQL Server and SQL Azure
ODBC Datasource May require change
User and Password May require change
Return on Success SQL_SUCCESS SQL_SUCCESS or SQL_SUCCESS_WITH_INFO
Return on Error SQL_ERROR SQL_ERROR
Error Check Code if(ret == SQL_SUCCESS) May require change
if(retcode != SQL_SUCCESS) May require change
if(retcode != SQL_ERROR)
if(retcode == SQL_ERROR)
if(retcode >= SQL_SUCCESS)
if(retcode => 0)
if(retcode <= -1)

Last Update: Microsoft SQL Server 2012 and Oracle 11g

Conversion Details

When you connect to Oracle using Oracle ODBC driver (sqora32.dll), the SQLConnect() function returns SQL_SUCCESS when the connection is successful.

At the same time, if you use SQL Server Native Client (native SQL Server ODBC driver) to connect to SQL Server, it returns SQL_SUCCESS_WITH_INFO when the connection is successful, and the message text contains: 

"[Microsoft][SQL Server Native Client 11.0][SQL Server]Changed database context to 'master'."

Note. SQL_SUCCESS_WITH_INFO is returned even if you do not specify to change the default database in the SQL Server ODBC driver settings.

Error Code Check

If your Oracle application checks SQL_SUCCESS after calling SQLConnect(), you have to change the code to also check for SQL_SUCCESS_WITH_INO, or just check for a value >= 0 for a successful connection, and < 0 for failed connection:

Oracle: 

   // Connect to Oracle
   SQLRETURN retcode = SQLConnect(hdbc, "db_dsn", SQL_NTS, "scott", SQL_NTS, "tiger", SQL_NTS);
 
   // Check if connection failed
   if(retcode != SQL_SUCCESS)
   {
      // ... exit
   }
 
   // Check if connection successful
   if(retcode == SQL_SUCCESS)
   {
      // ... continue processing
   }

SQL Server and SQL Azure: 

   // Connect to SQL Server
   SQLRETURN retcode = SQLConnect(hdbc, "db_dsn", SQL_NTS, "scott", SQL_NTS, "tiger", SQL_NTS);
 
   // Check if connection failed
   if(retcode < SQL_SUCCESS)   // changed != to < 
   {
      // ... exit
   }
 
   // Check if connection successful
   if(retcode >= SQL_SUCCESS)    // changed == to >=
   {
      // ... continue processing
   }

SQLines ODBC Driver for Oracle to SQL Server

SQLines ODBC driver supports the following conversion features for SQLConnect() function:

Using SQLines ODBC driver you do not need to modify existing Oracle ODBC applications that use SQLConnect() function. More...

Resources

Microsoft MSDN