MySQL only Which is why I'm still using Oyako ( https://github.com/briancarper/oyako )
A new version of oyako is coming soon-ish (within a week or two) with possible mysql support, but it will always focus primarily on postgresql. The next version will also feature an SQL DSL similar to ClojureQL but less fancy / magical. (ClojureQL looks pretty cool itself though.)
In my brief experience, the idea of a cross-database SQL DSL is a lost cause unless you want to limit yourself to a very small subset of SQL. Funny, for a language that supposedly has a standard.