update ... from where id in (..) question

Hi,

I have a table with approx. 2mln records.

There were a few for which I had to update statusfield, so I did:

update table set statusflag = 'U' where id in ('id10', 'id20',
'id30');

this took so long that I cancelled it, and used separate

update table set statusflag = 'U' where id = 'id10';

statements, which were executed in a fraction of a second.

Has someone an explanation for this ?

--
Feite Brekeveld
feite(dot)brekeveld(at)osiris-it(dot)nl