如何优化以下mysql查询？

Question

I have different category of data in my table. I want to count items in each section of category. Each section contains more than two categories.

How can i optimize this query?

SELECT s1,s2,s3,s4,s5,s6,s7,s8,s9,s10,s11,s12 
FROM (
  (SELECT count(category) as s1  FROM `category_data` WHERE `type` = '2' and category IN ('2','3','4','5','6','7')) AS t1,
  (SELECT count(category) as s2  FROM `category_data` WHERE `type` = '2' and category IN ('8','9','10','11','12')) AS t2,
  (SELECT count(category) as s3  FROM `category_data` WHERE `type` = '2' and category IN ('13','14','15','16','17')) AS t3,
  (SELECT count(category) as s4  FROM `category_data` WHERE `type` = '2' and category IN ('18','19','20','21','22')) AS t4,
  (SELECT count(category) as s5  FROM `category_data` WHERE `type` = '2' and category IN ('23','24','25','26','27')) AS t5,
  (SELECT count(category) as s6  FROM `category_data` WHERE `type` = '2' and category IN ('28','29','30','31','32')) AS t6,
  (SELECT count(category) as s7  FROM `category_data` WHERE `type` = '2' and category IN ('33','34','35','36','37')) AS t7,
  (SELECT count(category) as s8  FROM `category_data` WHERE `type` = '2' and category IN ('38','39','40','41','42')) AS t8,
  (SELECT count(category) as s9  FROM `category_data` WHERE `type` = '2' and category IN ('43','44','45','46','47')) AS t9,
  (SELECT count(category) as s10  FROM `category_data` WHERE `type` = '2' and category IN ('48','49','50','51','52')) AS t10,
  (SELECT count(category) as s11  FROM `category_data` WHERE `type` = '2' and category IN ('53','54','55','56','57')) AS t11,
  (SELECT count(category) as s12  FROM `category_data` WHERE `type` = '2' and category >= ('58')) AS t12
)

Answer 1

SELECT
SUM(category IN ('2','3','4','5','6','7')) AS s1,
...
SUM(category >= ('58')) AS s12
FROM
`category_data` 
WHERE `type` = '2'

Instead of reading the table multiple times you can do this just once.
I use SUM() instead of count, cause the boolean expression in it equals to true or false , 1 or 0 , which is then basically the same as counting.

Answer 2

You can use case as a mean to reduce the number of table references:

SELECT count(case when type = 2 and category IN ('2','3','4','5','6','7') then 1 end)
    ,  count(case when type = 2 and category IN ('8','9','10','11','12') then 1 end)
...
FROM `category_data

`

Answer 3

I think you should use partitioning on table "category_data" by category column. Have a look at http://dev.mysql.com/doc/refman/5.7/en/partitioning-types.html . You can partition it by LIST for ref. http://dev.mysql.com/doc/refman/5.7/en/partitioning-list.html .