query.str() not returning anything

[Kemin Zhou]

Has anyone seen this problem?

Query query=connection.query();
query << "some sql string";
try { query.execute(); } catch (exception &err)
{

cerr << query.str() << endl << err.what() << endl;


}

Nothing was outputted when there was an exception .
The err.what() will say something like:
You have an error in your SQL syntax; check the manual that corresponds 
to your MySQL server version for the right syntax to use near

Kemin