Establishing an ODBC Connection

Establish an ODBC connection in your application to perform any database operations.

1. Allocate an ODBC environment.

   For example:

   SQLRETURN rc;
   SQLHENV   env;
   rc = SQLAllocHandle( SQL_HANDLE_ENV, SQL_NULL_HANDLE, &env );

2. Declare the ODBC version.

   By declaring that the application follows ODBC version 3, SQLSTATE values and some other version-dependent features are set to the proper behavior. For example:

   rc = SQLSetEnvAttr( env, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0 );

3. Allocate an ODBC connection item.

   For example:

   rc = SQLAllocHandle( SQL_HANDLE_DBC, env, &dbc );

4. Set any connection attributes that must be set before connecting.

   Some connection attributes must be set before establishing a connection or after establishing a connection, while others can be set either before or after. The SQL_AUTOCOMMIT attribute is one that can be set before or after:

   rc = SQLSetConnectAttr( dbc, SQL_AUTOCOMMIT, (SQLPOINTER)SQL_AUTOCOMMIT_OFF, 0 );

   By default, ODBC operates in autocommit mode. This mode is turned off by setting SQL_AUTOCOMMIT to false.

5. If necessary, assemble the data source or connection string.

   Depending on your application, you may have a hard-coded data source or connection string, or you may store it externally for greater flexibility.

6. Call the ODBC connection function.

   For example:

   if (rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO) 
   {
      printf( "dbc allocated\n" );
      rc = SQLConnect( dbc,
         (SQLCHAR *) "Sybase IQ Demo", SQL_NTS,
         (SQLCHAR *) "<user_id>", SQL_NTS,
         (SQLCHAR *) "<password>", SQL_NTS );
      if (rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO)
      {
          // Successfully connected.

   Every string passed to ODBC has a corresponding length. If the length is unknown, you can pass SQL_NTS indicating that it is a Null Terminated String whose end is marked by the null character (\0).