d9ac568d_YPO3_Core_APIs_7_documentation__Description
[Class name] \TYPO3\CMS\Core\Database\DatabaseConnection [Usage] Available as $GLOBALS['TYPO3_DB'] in both frontend and backend [Description] 
Database Abstraction Base API All access to the database must go through this object. That is the first step towards DBAL compliance in your code. The class contains MySQL wrapper functions which can almost be search/replaced with your existing calls.
TYPO3 Core APIs 7 documentation
Description