CB

This is just a minor hardening, similar to what is proposed here: https://github.com/joomla/joomla-cms/pull/13825
Actually, it's only affecting the standalone Mysql driver as the Joomla one will be improved through the Joomla core.

Second case fix based on Joomla fix, based on many other similar fixes elsewhere and on MSSQL official doc at Microsoft, second case seems ok too:
https://technet.microsoft.com/en-us/library/ms176027(v=sql.105).aspx