In svn command, if you want rollback your code of svn server. you should use svn merge to merage new version and old version.
like :
svn merge -r newversion:oldversion
But if you want check out old version to cover new version. do like this:
svn co -r oldversion svnpath localpath
svn 如果是svn server的代码需要回滚，则使用svn merge -r newversion:oldversion
如果是svn客户端 check out出来的代码需要找到以前的版本，则使用svn co -r version svnpath localpath