Optimizing the index shows an example single MYSQL

1. Create a table　

CREATE TABLE IF NOT EXISTS `article` (
`id` BIGINT(10) NOT NULL AUTO_INCREMENT,
`author_id` INT(10) NOT NULL,
`category_id` INT(10) NOT NULL,
`views` INT(10) NOT NULL,
`comments` INT(10) NOT NULL,
`title` VARCHAR(10) COLLATE utf8_unicode_ci NOT NULL,
`content` TEXT COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

2. Add data

INSERT INTO article(author_id,category_id,views,comments,title, content)
VALUES (1,1,1,1,'1','1'), (2,2,2,2,'2','2'),(1,1,3,3,'3','3');

3. Query

SELECT * FROM article;

4. Demand

　　Query category_id case 1 is greater than 1 and comments, views the most article_id.

5. SQL

　　SELECT id, author_id FROM article WHERE category_id =1 AND comments>1 ORDER BY views DESC LIMIT 1;

6. index optimization analysis

　　type = ALL: full table scan

　　 key = NULL: do not use the index,

　　Extra also appeared Using filesort, had a secondary sorting

　　Conclusion: garbage, it needs to be optimized.

　　(1) for the first time to create an index

　　　　　First View original article index

　　　　It is a primary key primary index. And where, order by using the column did not have any relationship, so do not take the index to normal.

　　　　 The following create a multi-column index based on where, order by field

　　　　 create index idx_c_c_v on article(category_id,comments, views);

　　　　View index again　　　　

　　　 Note that the index inx_c_c_v, Seq_in_index indicates the index column for the order, more than, for example, said in use inx_c_c_v, first find category_id, find comments, and finally find views.

　　　　After creating the index, we then analyze SELECT id, author_id FROM article WHERE category_id = 1 AND comments> 1 ORDER BY views DESC LIMIT 1 of the implementation plan.