Many to many table queries

eid | fid
----+----
1   | A
1   | B
1   | C
2   | B
2   | C
3   | A
3   | C
4   | A
4   | B
5   | B

select t1.eid
  from t t1
 where t1.fid  = 'B'
   and not exists
       (select 1
          from t t2
         where t2.eid = t1.eid
           and t2.fid  = 'A')

Select eid from t where fid = 'B'
EXCEPT
select eid from t where fid = 'A'

SELECT DISTINCT t1.eid
FROM table1 AS t1
  LEFT JOIN table1 AS t2 ON (t1.eid = t2.eid AND t2.fid = 'A')
WHERE t2.eid IS NULL
  AND t1.fid = 'B';

SELECT DISTINCT t1.eid
FROM table1 AS t1
  LEFT JOIN table1 AS t2 ON (t1.eid = t2.eid AND t2.fid = 'A')
WHERE t2.eid IS NULL
  AND t1.fid = 'B';

select eid
from t
where fid = 'A'
minus
select eid
from t
where fid = 'B'