Question

我的表中有不同类别的数据。我想计算每个类别中的项目。每个部分包含两个以上的类别。

如何优化此查询？

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'

您可以多次阅读该表，而不是多次阅读该表我使用SUM()而不是count，因为它中的布尔表达式等于true或false，1或0，这基本上与计数。

Answer 2

您可以使用大小写来减少表引用的数量：

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

我认为你应该在表格上使用分区＆＃34; category_data＆＃34;按类别列。看看http://dev.mysql.com/doc/refman/5.7/en/partitioning-types.html。您可以通过LIST对其进行分区以进行参考。 http://dev.mysql.com/doc/refman/5.7/en/partitioning-list.html

如何优化以下mysql查询？

3 个答案: