>>>>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"
>
>What version of VFP?
>How about (Just in case you use VFP9):
>

>update mytable set flag = "1";
>       FROM mytable;
>INNER JOIN (SELECT f1 from look_up group by f1 having count(*) = 1) Tbl1 ON MyTable.F1 = Tbl1.F1
>INNER JOIN (SELECT f2 from look_up group by f2 having count(*) = 1) Tbl2 ON MyTable.F2 = Tbl1.F2
>

He-he <g> That's what I suggested in the first place (was a bit lazy to write the whole thing, though).