>>This works
>>

>>SELECT * FROM mytable where;
>> f1 in (SELECT f1 from look_up group by f1 having count(*) = 1) AND ;
>> f2 in (select f2 from look_up group by f2 having count(*) = 1)
>>

>>
>>and this fails
>>

>>update mytable set flag = "1" where;
>> f1 in (SELECT f1 from look_up group by f1 having count(*) = 1) AND ;
>> f2 in (select f2 from look_up group by f2 having count(*) = 1)
>>

>
>And you are very sure that the SELECT returns correct record but UPDATE didn't update all of them?
>What happens with this:
>

>update mytable set flag = "1";
>FROM mytable;
> where f1 in (SELECT f1 from look_up group by f1 having count(*) = 1) AND ;
>       f2 in (select f2 from look_up group by f2 having count(*) = 1)
>

the select works fine, the update give the error "sql statement too complex"