Puzzled,

I simplyfied a table update which took forever to the following

Using IB_WISQL

create table ta (a integer not null, b integer,
primary key (a))

create table tb (a integer not null, b integer,
primary key (a))

Now

update ta set ta.b =
(select tb.b from tb where tb.a = ta.a)

generates

PLAN (TB NATURAL)
PLAN (TA NATURAL)

Of course without any indexes this could take some time, but why ?

Best Regards
Hans