In the QODBCDriverPrivate::checkUnicode() method, the query QLatin1String("select 'test'")) attempts to determine whether the database supports Unicode. 
SELECT without FROM is not standard-compliant. DB2 and Oracle do not allow a query without FROM.

Possible solution:
At least DB2 supports the values('test') statement.
Possible solution (but not the nicest):
r = SQLExecDirect(hStmt, toSQLTCHAR(QLatin1String("select 'test'")).data(), SQL_NTS); if(r != SQL_SUCCESS) r = SQLExecDirect(hStmt, toSQLTCHAR(QLatin1String("values('test')").data(), SQL_NTS);