SQL (or to be more precise, the RDBMS) is not meant to be the right choice for formatting the output. The database should deliver raw data which then should be formatted (or more general: processed) in the destination application.
However, depending on the specific system you use, you may write a UDF (user defined function) to achive what you want. But please bear in mind that you then are in fact returning a varchar, which you will not be able to further process (e.g. summarize).