SQLite Forum: How to select entries from second table that either do not have an entry or do not have a specific entry?

For example:<code>
 create table One (A integer);
 create table Two (A integer, B text);
 insert into One values (100);
 insert into One values (101);
 insert into One values (102);
 insert into Two values (100, 'X');
 insert into Two values (100, 'Y');
 insert into Two values (100, 'Z');
 insert into Two values (101, 'Y');
 insert into Two values (101, 'Z');
 select A from One except select A from Two where Two.B in ('X');
</code>