From the ADOdb website and developer sites, it supports the following databases:
ADOdb uses SQL. Since each database implements SQL slightly differently, the developer will need to be aware of the database-specific features and functions to avoid if they want to maintain portability. ADOdb provides date conversion functions so that you can create dates in any format and insert them into your SQL in the correct format for your database; which is one step toward database independent SQL.
Some databases support the Limit phrase which first appeared in MySQL and is now part of SQL. ADOdb's SelectLimit() translates limit to different mechanisms for each database and can emulate limit for databases with no native limit equivalent. Translations will perform efficiently. Emulations may work slowly by returning too many rows then using only those that meet the limit.
ADOdb has variables that contain the correct SQL for a database for specific functions. For example, to check for a null value, null can be replaced with the ADOdb variable that contains the correct SQL definition for null and the check for null will work in every database.