Need to get success ratio for clients - sql

Question

I had a really nice guy in FreeNode IRC steer me closer to the answer.
The query I am using now is:
SELECT st.staff_id
, ROUND (100.0 * ( sum (case when s.code in ('10401','10402','10403') then 1
else 0 end)/count(s.code)), 1) as successes
from notes n join services s on n.zrud_service=s.zzud_service
join staff st on n.zrud_staff = st.zzud_staff
WHERE s.code IN ( '10401','10402','10403','10405')
AND n.date_service BETWEEN (now() - '30 days'::interval)::timestamp AND now()
group by st.staff_id;
(I did try /count(*) as well as a few other ways)
It does not error, and shows the results as either 100.0 or 0
I ran a query on just the codes grouped by staff and get different results. One staff discharged 23 people in the past month, 8 being unsuccessful (10405) This gives a percentage of 34.7% success rate. But the query shows 0%.
This is baffling. Anyone have suggestions?
Original question
I need to be able to see what percentage of successful discharges there are in a 30 day period. Here is a query that shows the discharges by code. I understand that I can use a "division" method in postgresql, but I have only been able to use it with two separate columns. Can someone assist in showing me how to divide data within a column?
I need to do something like: 10401'+'10402'+'10403' / 10401'+'10402'+'10403'+'10405'
SELECT n.date_creation, g.name AS Group, s.staff_id, n.date_service, c.client_id,
c.name_lastfirst_cs AS Client, q.code
FROM notes n, clients c, groups g, staff s,services q
WHERE n.visibility_flag = 1 -- valid note
AND notes.date_service BETWEEN (now() - '30 days'::interval)::timestamp AND now();
AND c.zzud_client = n.zrud_client AND n.zrud_group = g.zzud_group
AND n.zrud_staff = s.zzud_staff
AND q.code IN ('10401','10402','10403','10405') -- 10405 is unsuccessful discharge
AND n.zrud_service = q.zzud_service AND n.zrud_staff = ? ORDER BY n.date_service
If I re-write the query as such:
SELECT g.name AS Group, s.staff_id, c.client_id,
c.name_lastfirst_cs AS Client, q.code
FROM notes n, clients c, groups g, staff s,services q
WHERE n.visibility_flag = 1 -- valid note
AND notes.date_service BETWEEN (now() - '30 days'::interval)::timestamp AND now();
AND c.zzud_client = n.zrud_client AND n.zrud_group = g.zzud_group
AND n.zrud_staff = s.zzud_staff
AND n.zrud_service = q.zzud_service AND n.zrud_staff = ? ORDER BY n.date_service
OR, Instead of all the +'s, could I use the "SUM" operator?
I changed the query to:
SELECT g.name AS Group, s.staff_id AS Staff
SUM(CASE WHEN q.code BETWEEN '10401' AND '10405' THEN 1 ELSE 0 END) / SUM(CASE WHEN q.code BETWEEN '10401' AND '10405' THEN 0 ELSE 1 END)
AS success_ratio FROM FROM notes n, clients c, groups g, staff s,services q
AND n.date_service BETWEEN (now() - '30 days'::interval)::timestamp AND now()
AND q.code IN ('10401','10402','10403','10405')
AND c.zzud_client = n.zrud_client AND n.zrud_group = g.zzud_group
AND n.zrud_staff = s.zzud_staff
AND n.zrud_service = q.zzud_service AND s.staff_id = 'BATTNEAL1026' ORDER BY n.date_service
GROUP BY s.staff_id
And get this error:
ERROR: syntax error at or near "SUM"
LINE 2: SUM(CASE WHEN q.code BETWEEN '10401' AND '10405' THEN 1 ELSE...
^
********** Error **********
ERROR: syntax error at or near "SUM"
SQL state: 42601
Character: 45

Answer 1

Your problem is the division with two bigint / integer numbers. Since your result is always < 0, this results in either 0 or 1. Here:
sum (case when s.code in ('10401','10402','10403') then 1 else 0 end)
/count(s.code)
Multiply by 100.0 first.
The fractional digit in 100.0 coerces the calculation to be done in numeric, which preserves the fractional part.
With some other modifications and formatting, it could look like this:
SELECT st.staff_id
,round((count(s.code IN ('10401','10402','10403') OR NULL) * 100.0)
/ count(*), 1) AS successes
FROM notes n
JOIN services s ON s.zzud_service = n.zrud_service
JOIN staff st ON st.zzud_staff = n.zrud_staff
WHERE s.code IN ('10401','10402','10403','10405')
AND n.date_service BETWEEN (now() - '30 days'::interval) AND now()
GROUP BY st.staff_id;