选择合适的索引 技巧: 对查询频繁使用的列创建合适的索引(单列索引、组合索引等)。 案例: 问题SQL: SELECT name FROM employees WHERE department_id 10; 优化: 为department_id创建索引: CREATE INDEX idx_department_id ON employees(dep…
要实现对 descrlong1 字段的多选查询,可以使用 SQL 的 IN 或 LIKE 语法,具体取决于数据存储方式和需求。查询包含特定关键词的记录,以下是两种常见的方法: 使用 LIKE
如果数据是以逗号分隔的字符串存储在 descrlong1 字段中&…
云镜像下载网址 CentOS Cloud images (centos)Ubuntu Cloud Images (ubuntu)https://virtualization.kubesphere.cloud/images/ Index of /mirror/cdimage/openstack/archive (debian)http://download.cirros-cloud.net/ Index …
E. Strongly Connected City
Imagine a city with n horizontal streets crossing m vertical streets, forming an (n - 1) (m - 1) grid. In order to increase the traffic flow, mayor of the city has decided to make each street one way. This means in each h…