Mysql split row sum by count - mysql

Question

I have the following tables
http://sqlfiddle.com/#!2/d0a3d
sp | product | exp
1 A | 50
1 B 50
1 A 100
1 B 100
2 B 200
2 C 200
3 A 50
3 B 50
Technical I want to divide exp to total number of products associated with t_id
The final result should be
sp | A | B | C
1 | 150 | 150 | 0
2 | 0 | 200 | 200
3 | 50 | 50 | 0

Answer 1

Can be done like this (done to match your sql fiddle columns):-
SELECT b.sp_id,
SUM(IF(a.product = 'A', b.exp, 0)) AS A,
SUM(IF(a.product = 'B', b.exp, 0)) AS B,
SUM(IF(a.product = 'C', b.exp, 0)) AS C
FROM topic_product a
INNER JOIN exp_speaker_topic b
ON a.t_id = b.t_id
GROUP BY b.sp_id
But a mess waiting to happen when extra values get added.
EDIT - amended to give what I think you are saying you want.
SELECT sp_id,
SUM(IF(product = 'A', avg_exp, 0)) AS A,
SUM(IF(product = 'B', avg_exp, 0)) AS B,
SUM(IF(product = 'C', avg_exp, 0)) AS C
FROM
(
SELECT sp_id, a.product, exp / Sub1.product_count AS avg_exp
FROM topic_product a
INNER JOIN exp_speaker_topic b
ON a.t_id = b.t_id
INNER JOIN
(
SELECT t_id, COUNT(*) AS product_count
FROM topic_product
GROUP BY t_id
) Sub1
ON a.t_id = Sub1.t_id
) Sub2
GROUP BY sp_id
SQL fiddle:-
http://sqlfiddle.com/#!2/d0a3d/33

Answer 2

OK, slow day. Just do the following, and handle missing results and display logic in the presentation layer/application-level code (e.g. a simple php loop acting upon an ordered array)...
SELECT p.product
, s.sp_id
, SUM(s.exp/x.cnt) total
FROM topic_product p
JOIN exp_speaker_topic s
ON s.t_id = p.t_id
JOIN
( SELECT t_id
, COUNT(0) cnt
FROM topic_product
GROUP
BY t_id
) x
ON x.t_id = p.t_id
GROUP
BY sp_id,product;

Answer 3

Here is the SQL Fiddle demonstrating the below queries.
You could also use CASE statements like the following:
SELECT e.sp_id,
SUM(CASE WHEN t.product = 'A' THEN e.exp ELSE 0 END) AS A,
SUM(CASE WHEN t.product = 'B' THEN e.exp ELSE 0 END) AS B,
SUM(CASE WHEN t.product = 'C' THEN e.exp ELSE 0 END) AS C
FROM topic_product t INNER JOIN exp_speaker_topic e ON t.t_id = e.t_id
GROUP BY e.sp_id;
If you want to divide by the number of record use the following:
SELECT e.sp_id,
SUM(CASE WHEN t.product = 'A' THEN e.exp ELSE 0 END) /
SUM(CASE WHEN t.product = 'A' THEN 1 ELSE 0 END) AS A,
SUM(CASE WHEN t.product = 'B' THEN e.exp ELSE 0 END) /
SUM(CASE WHEN t.product = 'B' THEN 1 ELSE 0 END) AS B,
SUM(CASE WHEN t.product = 'C' THEN e.exp ELSE 0 END) /
SUM(CASE WHEN t.product = 'C' THEN 1 ELSE 0 END) AS C
FROM topic_product t INNER JOIN exp_speaker_topic e ON t.t_id = e.t_id
GROUP BY e.sp_id;
If you want to get rid of the Nulls you could use the following:
SELECT m.sp_id,
CASE WHEN ISNULL(m.A) = 0 THEN m.A ELSE 0 END AS A,
CASE WHEN ISNULL(m.B) = 0 THEN m.B ELSE 0 END AS B,
CASE WHEN ISNULL(m.C) = 0 THEN m.C ELSE 0 END AS C
FROM
(
SELECT e.sp_id,
SUM(CASE WHEN t.product = 'A' THEN e.exp ELSE 0 END) / SUM(CASE WHEN t.product = 'A' THEN 1 ELSE 0 END) AS A,
SUM(CASE WHEN t.product = 'B' THEN e.exp ELSE 0 END) / SUM(CASE WHEN t.product = 'B' THEN 1 ELSE 0 END) AS B,
SUM(CASE WHEN t.product = 'C' THEN e.exp ELSE 0 END) / SUM(CASE WHEN t.product = 'C' THEN 1 ELSE 0 END) AS C
FROM topic_product t INNER JOIN exp_speaker_topic e ON t.t_id = e.t_id
GROUP BY e.sp_id
) AS m;