Mysql - Help for optimizing query - mysql

Question

I have this query:
SELECT bi.id,
bi.location,
bi.expense_group,
bi.level,
bi.is_active,
bi.type,
full_name,
( bl.bud_amount ) AS BudgetAmount,
( COALESCE(( ( bl.bud_amount * 3 ) - (
+ bal.bal_amount1 + bal.bal_amount2
+ bal.bal_amount3 ) ), 0) ) AS Difference,
( COALESCE(Round(( + bal.bal_amount1 + bal.bal_amount2
+ bal.bal_amount3 ) / 3), 0) ) AS Average,
bal.bal_amount1 AS BAL1,
bal.bal_amount2 AS BAL2,
bal.bal_amount3 AS BAL3
FROM (SELECT *
FROM budget_items bi
WHERE bi.location IS NOT NULL) AS bi
LEFT JOIN (SELECT budget_item_id,
Sum(CASE
WHEN budget_id = 21491 THEN amount
END) AS bud_amount
FROM budget_lines
GROUP BY budget_item_id) AS bl
ON bl.budget_item_id = bi.id
JOIN (SELECT budget_item_id,
Ifnull(Sum(CASE
WHEN balance_id = 12841 THEN amount
END), 0) AS bal_amount1,
Ifnull(Sum(CASE
WHEN balance_id = 18647 THEN amount
END), 0) AS bal_amount2,
Ifnull(Sum(CASE
WHEN balance_id = 18674 THEN amount
END), 0) AS bal_amount3
FROM balance_lines
GROUP BY budget_item_id) AS bal
ON bal.budget_item_id = bi.id
ORDER BY bi.location
It takes a lot of time. In the budget_lines and balance_lines tables I have more than 5,000,000 rows in each.
I also attach the EXPLAIN of the query, so you'll ne able to see the problem.
All ids in every table are indexed. Is there any column that if would be indexed spped up the query? Or maybe I need to change it.
*** LEFT JOIN is necessary because I need to get all the items from nudget_items, even if they don't exist in the balance/budget_line table.
Schema is: every budget has its budget_lines. Every balance has its balance_lines. The query is aimed to have ONE table to summarize the differences between a budget and several balances.
You can see a bigger image here: http://i.stack.imgur.com/dlF8V.png
EDIT:
After #Sebas answers:
For #sabes hunger, I put here the DESCRIBE:
budget_items
budget_lines
balance_lines

Answer 1

Maybe something like this; but without sample data, and indexes it's difficult to see
SELECT *
FROM budget_items bi
WHERE bi.location IS NOT NULL) AS bi
INNER JOIN --Added inner for clarity -changed order I just like my inner's before my outers.
(SELECT budget_item_id, Sum(CASE WHEN balance_id = 12841 THEN coalesce(amount,0) END), 0) AS bal_amount1,
Sum(CASE WHEN balance_id = 18647 THEN coalesce(amount,0) END), 0) AS bal_amount2,
Sum(CASE WHEN balance_id = 18674 THEN coalesce(amount,0) END), 0) AS bal_amount3
FROM balance_lines
WHERE balance_ID in (12841, 18647, 18674) --This way balance_IDs which aren't in this list don't even get evaluated
GROUP BY budget_item_id) AS bal
ON bal.budget_item_id = bi.id
LEFT JOIN
(SELECT budget_item_id, Sum(CASE WHEN budget_id = 21491 THEN coalesce(amount,0) END) AS bud_amount
FROM budget_lines
WHERE budget_Id = 21491 --Again since we only care about anything but budget_ID 21491, we can limit the results to JUST that
GROUP BY budget_item_id) AS bl
ON bl.budget_item_id = bi.id