see
MySQl's website for details
as regards for soemhting that oracle does that MySQL can't...now that could be tricky
the best way would be to look at things that Orcale does that isnt according to the ANSI SQL standard, or equally soemthign that MySQL doesnt do according to the same standard
One thing mySQL doesnt handle correctly is a grouping statement
in MySQl its valid to do something like
select colum,n1,column2,column3,sum(column4) as sumcolumn4 group by Column3, whereeas as the standard insists that you must have all the the columns selected in the group by expression
there are lots of other permutations, however I think it comes down to what the heck the requirement is. if you need 'big' discrepancies then you may need to work a lot harder, but my copuy of SQL in a nutshell (pub O'Reilly) has ots of discrepancies listed... however it was published in 2001, and was comparing MySQL 3.22.9 and Oracle 8.1... both have moved on since then, arguably MySQL has moved the furtherest.
If I were you Id do a google and try to do some searching of your own. A word of caution though, many peoples comments in thsi field are going to be limited by their own knwoledge, experiences, and in some cases prejudices... if you work with one database (and realistically you cant be an expert in all SQL databases [unless of course you are someone of Rudy's experience]) then you tend to be expert in that. some people cite software vendors marketing materail as gospel. Some people hold second hand comments as fact (where they are quoting facts discovered by someonelse years ago), or when they last looked at MySQL ...say years ago). I still hear statements that MySQL doesn't support stored procdures, referential integrity and a host of other features introduced since MySQL launched V5.
when you cite a discrepancy make sure you tie down the verison number of mySQL & oracle they are talking about.
One very very sneaky technique could be to compare the most recent Oracle/MySQL offering with the earliest MySQL/Oracle offering you can track down.