I have problems figuring out how to alter SET and ENUM types in mySQL.

It's a snap in phpMyAdmin, but if I build a CMS for a client, I won't let him use that ;-).

Funny thing is, although most commands are echo'd in phpMyAdmin, altering SET and ENUM columns do not return anything.

these SELECT statements all work perfectly:

select * where cat.name = 'foo':
SELECT * FROM table WHERE (Kat='foo');

select * where cat.name NOT 'foo':
SELECT * FROM table WHERE FIND_IN_SET('foo',Kat)<1;

select * where cat.name neither 'foo' nor 'bar':
SELECT * FROM table WHERE (FIND_IN_SET('Konsum',Kat)<1) AND (FIND_IN_SET('POS',Kat)<1)
(0=false, 1=true)

OK, but what about *altering* the SET's? Removing a SET item, adding one, or renaming?
On the mySQL manual page there's this syntax posted in the user-contributions:

UPDATE table SET myCol = concat(myCol, ',additional item')

for adding one SET item, but that doesn't work.

I tried different commands, with ALTER TABLE, UPDATE, and what not, but none is working.

It's a shame there is so little mention of altering ENUM and SET columns in the official manual, considering how useful these datatypes are (or rather - could be).

Oh, and on a similar subject:
Does anyone know what the MAJOR difference is between SET and ENUM (preferrably from a real-life scenario point of view)? SET can have only 64 members, whereas ENUM can have 65535 elements. So why would I limit myself to only 64 entries with a SET?

Any and every sample syntax, link, and help is highly appreciated.