INDEX `article_id`(`article_id`)
时间: 2023-10-23 07:14:55 浏览: 123
This is an index that is created on the column `article_id` in a database table. It is used to improve performance when searching, sorting or joining data on this column. When the index is created, the database engine creates a separate data structure that contains a sorted list of all the values in the `article_id` column, along with a pointer to the location of the corresponding record in the table. This allows the database to quickly find and retrieve records based on the article_id value, without having to scan the entire table.
相关问题
user_click_count = user_click_merge.groupby(['user_id', 'click_article_id'])['click_timestamp'].agg({'count'}).reset_index()这句话是什么意思
这句话的意思是,对于一个名为 user_click_merge 的数据集,按照用户 ID 和点击的文章 ID 进行分组,然后计算每个用户对每篇文章的点击次数,并将结果存储在一个名为 count 的新列中。最后,将结果存储在一个新的数据集中并返回。
SELECT article_id, channel_name, SUM(IF(type = '0', 2, 0) + IF(type = '1', 2, 0) + IF(type = '2', 3, 0)) AS score FROM leadnews_article.user_record WHERE request_time > '2025-05-06' AND channel_name = 'ps4' GROUP BY article_id ORDER BY score LIMIT 10; 如何建立联合索引
可以使用以下SQL语句建立联合索引:
```
CREATE INDEX idx_user_record ON leadnews_article.user_record(request_time, channel_name, type, article_id, score);
```
这样的话,查询语句中涉及到的字段都可以使用这个联合索引,包括request_time, channel_name, type, article_id和score。在执行查询语句时,数据库会根据索引的顺序进行查询,可以大大提高查询效率。