Reduce execution time of query - mysql

Question

I want to reduce the time taken by the query in mysql.
There are three tables say
A ~600k rows,
B ~2K rows,
C ~100K rows
having 2 columns each.
A has one column which is used in aggregation and other to join with table B.
B has one column to join with A and other with C
C has one column to join with B and other column to group by.
What should be the indexing plan to reduce the run time. As of now it is using temporary tables and then file sort. Is there any way we could avoid temporary tables.
Sample query :
SELECT
sum(`revenue_facts`.`total_price`) AS `m0`
FROM
`category_groups` AS `category_groups`,
`revenue_facts` AS `revenue_facts`,
`dim_products` AS `dim_products`
WHERE
`dim_products`.`product_category_group_sk` = `category_groups`.`product_category_group_sk` AND
`revenue_facts`.`product_sk` = `dim_products`.`product_sk`
GROUP BY `category_groups`.`category_name`;
I already have indexes on group by column and the columns in join.
my query is currently taking *6 minute*s. I want to reduce the time taken. table structure is as
table A :
CREATE TABLE `revenue_facts` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`product_sk` bigint(20) unsigned NOT NULL,
`total_price` decimal(12,2) NOT NULL,
PRIMARY KEY (`id`),
KEY `product_sk` (`product_sk`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Table B :
CREATE TABLE `dim_products` (
`product_sk` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`product_category_group_sk` bigint(20) unsigned NOT NULL,
PRIMARY KEY (`product_sk`),
KEY `product_id` (`product_id`),
KEY (`product_sk`) (`product_sk`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
table C :
CREATE TABLE `category_groups` (
`product_category_group_sk` bigint(20) unsigned NOT NULL,
`category_sk` bigint(20) unsigned NOT NULL,
`category_name` varchar(255) NOT NULL,
PRIMARY KEY (`product_category_group_sk`,`category_sk`),
KEY `category_sk` (`category_sk`),
KEY `product_category_group_sk` (`product_category_group_sk`
KEY `category_sk` (`category_name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Execution plan used is:
1 SIMPLE dim_products index PRIMARY,product_category_group_index product_category_group_index 8 NULL 651264 Using index; Using temporary; Using filesort
1 SIMPLE category_groups ref PRIMARY,category_sk,product_category_group_sk,category_name product_category_group_sk 8 etl_testing.dim_products.product_category_group_sk 4 Using index
1 SIMPLE revenue_facts ref product_sk product_sk 8 etl_testing..dim_products.product_sk 5 NULL

Answer 1

Try this:
SELECT
sum(`revenue_facts`.`total_price`) AS `m0`
FROM
(`dim_products` LEFT JOIN `category_groups` ON `dim_products`.`product_category_group_sk` = `category_groups`.`product_category_group_sk`)
LEFT JOIN `revenue_facts` ON `dim_products`.`product_sk` = `revenue_facts`.`product_sk`
GROUP BY `category_groups`.`category_name`;
Also, as Abdul said:
"Post your table structures and explain plan"