Informix SQL count() comparisons

Question

I'm trying to build a SQL query that will count both the total number of rows for each id, and the number of 'FN%' and 'W%' grades grouped by id. If those numbers are equal, then the student only has either all 'FN%' or all 'W%' or a combination of both.

I need a list of all the id's who only have stats of 'FN%' or 'W%'

example id # 683 & 657 would make it into the result set of the query, but 603, 781 & 694 would not

   id stat
  683 WF
  683 WF
  683 WF
  683 WF
  683 W
  683 W
  657 W
  657 W
  657 W
  657 W
  781 B+
  781 IP
  781 WP
  781 WP
  603 FN
  603 FN
  603 F
  603 FN
  603 FN
  694 B
  694 B+
  694 CI
  694 LAB
  694 WF
  694 WF

sample output:

683
657

Answer 1

Here are two possible solutions that I can think of. I'm not sure if they'll work in Informix:

SELECT  id
FROM    foo a
GROUP   BY id
HAVING  COUNT(*) = (
                SELECT  COUNT(*)
                FROM    foo b
                WHERE   a.id = b.id
                AND     (b.stat LIKE 'FN%' OR b.stat LIKE 'W%')
        );

And if subqueries in the HAVING clause are verboten, maybe this will work instead:

SELECT  id
FROM    (
                SELECT  id, COUNT(*) stat_count
                FROM    foo
                WHERE   (stat LIKE 'FN%' OR stat LIKE 'W%')
                GROUP   BY id
        ) a
WHERE   stat_count = (SELECT COUNT(*) FROM foo b WHERE a.id = b.id);

Update: I just tried these in Oracle, and both work.

Answer 2

That explanation makes my head hurt. Are you looking for the union of these two sets?

• ids which only have stats matching "W%"
• ids which only have stats matching "FN%"

If that's the case, make it a UNION query with a sub-query for each of the sets.

Answer 3

Where xxxx is the temp table that holds this info to be processed.....

select id, fullname, count(id) ttl 
from xxxx 
group by id, fullname 
into temp www with no log;


select id, fullname, count(id) ttl_f 
from xxxx 
where grd like 'FN%' or grd like 'W%' 
group by id, fullname 
into temp wwww with no log;


select www.id, www.fullname 
from www, wwww 
where www.id = wwww.id and www.ttl = wwww.ttl_f;

Answer 4

This was written against the original question:

select first 50
c.id,
(select trim(fullname) from entity where id = c.id) fullname,
count(*),
(select count(*) from courses where id = c.id and grd like 'FN%') FN,
(select count(*) from courses where id = c.id and grd like 'W%') W
from courses c
group by 1

The subquery to retrieve the name is much faster than using a join for some reason.

Edit: The following will have the same behavior as yukondude's answer but performs better on our HPUX / Informix v10.00.HC5 box.

select c.id
from courses c
where not exists (
        select id
        from courses
        where (grd not like 'W%' and grd not like 'FN%')
        and id = c.id
)
group by 1