29DCH的博客

一般架构为主从数据库服务器搭配，例如一台Master(主服务器)对应着十几台或者上百台Slave(从服务器)，如果没有高可用的主从复制组件的话，当主服务器遇到意外情况崩溃时，很难自动进行故障切换，必须由DBA手动从众多从服务器中选择数据最新的提升为主服务器，其他从服务器再对这个新主服务器进行同步，这个过程又耗时间有占用大量主服务器的网卡容量．　　数据库服务器的性能指标：QPS & TPS...

druid是阿里开源的一个性能极佳的数据库连接池，详细介绍就不说了，可以自行了解。想读源码的话可以去github上面找阿里开源 https://github.com/alibaba/druid1.pom.xml文件加入如下依赖： <dependency> <groupId>com.alibaba&am

组合两个表https://leetcode-cn.com/problems/combine-two-tables/select a.FirstName,a.LastName,b.City,b.State from Person a LEFT JOIN Address b on a.PersonId=b.PersonId第二高的薪水https://leetcode-cn.com/p...

Employees Earning More Than Their Managershttps://leetcode.com/problems/employees-earning-more-than-their-managers/# Write your MySQL query statement belowselect e1.Name as Employeefrom Employe...

Delete Duplicate Emailshttps://leetcode.com/problems/delete-duplicate-emails/delete p1from Person p1, Person p2 where p1.Email=p2.Email and p1.Id>p2.Iddelete from Personwhere Id not in ...

Human Traffic of Stadiumhttps://leetcode.com/problems/human-traffic-of-stadium/select s.id,s.date,s.people from stadium s where people >= 100 and( ( (select people from stadium whe...