Use whereis can not find the file in the Mac
whereis uses a hardcoded list of paths to search. which uses your PATH.

/usr/local/mysql/bin isn't a standard location for binaries, so whereis doesn't search there. Presumably you've added that folder to your path (or the installer did), which means when which searches through your path folders, it finds it.

You can print the list of paths whereis searches by running the following:

$ sysctl user.cs_path
user.cs_path: /usr/bin:/bin:/usr/sbin:/sbin


Whereas your $PATH will generally have many more components. You can print your PATH with:

$ echo $PATH