pointers to sql standard, or "most common" sql?

So, I was trying to figure out which was close to standard sql:

     select * from foo limit 10
or
     set rowcount 10 select * from foo

and couldn't find much relevant information via google.

Is the sql standard on the web, and is there some document
about the syntax variations between sybase, oracle,
mysql, and postgresql?

Many TIA!

Mark