how to achieve mysql joining with conditional statement - mysql

Question

Hello I am thirst to get help as I am stuck for two days on a complex logical query,if anybody can help to solve.
Order Table
id | region_id | created_at | sale
=============|=============|=========================
1 | 1 | 2011-09-21 | $250
2 | 2 | 2012-03-12 | $320
3 | 1 | 2010-09-15 | $300
4 | 2 | 2011-08-18 | $180
5 | 1 | 2012-04-13 | $130
6 | 3 | 2010-06-22 | $360
7 | 2 | 2011-09-25 | $330
Regions Table
id | region_name
=============|=============
1 | Region 1
2 | Region 2
3 | Region 3
Expected Output
What I have tried to achieve
select distinct `regions`.`region_name`, sum(orders.sale) as sum,
CASE WHEN MONTH(orders.created_at)>=4 THEN
concat(YEAR(orders.created_at), '-',YEAR(orders.created_at)+1)
ELSE concat(YEAR(orders.created_at)-1,'-', YEAR(orders.created_at))
END AS financial_year from `orders` inner join `regions` on `orders`.`region_id` = `regions`.`id` group by YEAR(orders.created_at), `regions`.`region_name` order by `orders`.`region_id` asc, YEAR(orders.created_at) asc
My Queries Output
Where is my logical problem in query,one thing data should be fetched financial year wise not only normal year wise.
Thanks

Answer 1

http://sqlfiddle.com/#!9/16fdfb/9
Just to fix your query you should not use GROUP BY YEAR since your financial year does not match to calendar year, and since you don't want output different financial year in different rows but in columns. You can transform your query to:
SELECT regions.region_name,
o.salePrev as `2010-11`,
o.saleCurrent as `2011-12`
FROM (SELECT
region_id,
SUM(IF(MONTH(orders.created_at)<4,sale,0)) salePrev,
SUM(IF(MONTH(orders.created_at)>=4,sale,0)) saleCurrent
FROM orders
GROUP BY region_id
) o
INNER JOIN regions
ON o.region_id = regions.id;
But as I mentioned in my comment, your condition MONTH(orders.created_at)<4 is year independent I would transform it into something like:
SELECT regions.region_name,
o.salePrev as `2010-11`,
o.saleCurrent as `2011-12`
FROM (SELECT
region_id,
SUM(IF(
(MONTH(orders.created_at)<4 && YEAR(orders.created_at) = 2012)
|| YEAR(orders.created_at) < 2012
,sale,0)) salePrev,
SUM(IF(MONTH(orders.created_at)>=4 && YEAR(orders.created_at) = 2012,sale,0)) saleCurrent
FROM orders
GROUP BY region_id
) o
INNER JOIN regions
ON o.region_id = regions.id;
But yes it does not group by year, that just group current (2012-04 +) year against all the past years (2012-04 -).
If you need all years...
UPDATE http://sqlfiddle.com/#!9/16fdfb/17
SELECT r.region_name,
SUM(IF(o.f_year=2010,o.y_sale,0)) as `2010-11`,
SUM(IF(o.f_year=2011,o.y_sale,0)) as `2011-12`,
SUM(IF(o.f_year=2012,o.y_sale,0)) as `2012-13`
FROM (SELECT
region_id,
IF(MONTH(orders.created_at)<4,YEAR(created_at)-1,YEAR(created_at)) f_year,
SUM(sale) y_sale
FROM orders
GROUP BY region_id, f_year
) o
INNER JOIN regions r
ON o.region_id = r.id
GROUP BY r.id