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1,const Indicates that the execution step returns at most one row of data. const usually appears in the equivalent query of the primary key or unique index, such as the equivalent query of the primary key id of the t table:It can be considered that it is as fast as a rocket to locate a record by comparing the equivalence between the primary key ...

Java mentions the persistence layer framework. I believe no one doesn't know the existence of mybatis. Compared with JDBC, it has a more capable (JDBC workload is large), and compared with Hibernate, it has a more flexible (although HQL is convenient, it is too inflexible). Today we are going into her world together. 1, Simple implementation o ...

Source code: GitHub point here || GitEE point here 1, Scenario analysis 1. Scenario case Friends in the Internet industry must have known or heard of the following scenarios: Ali: thousands of thousands of faces, meaning different users use Ali related products feel different, for example, the recommended content of Alipay home page, and other ...

IDEA Connect to MySQL Database Add MySQL database connector to project Using mysql-connector-java-8.0.15.jar as an example, add jar files to your project The JDBC-MySQL connector is now added successfully Create the appropriate connection Connect the corresponding class in the jar file try { ...

For the source code of this tutorial, please visit: tutorial_demo In the previous tutorial, we used pure annotation and Apache Commons DbUtils to implement CRUD operation of single table, but the operation in this tutorial does not support transaction. In this tutorial, we changed it to transaction support version according to the existing kno ...

No matter what kind of service, its optimization is nothing more than from two aspects, the first is the optimization of hardware, the second is the optimization of the system and the service itself.1, Query the number of times to connect to the MySQL server mysql> show status like 'connections'; +---------------+-------+ | Variable_name | ...

In the Data Guard environment, there are two types of role switching for databases, Switchover and Failover. According to the name, the former is a normal role switching between the active and standby databases, which will not lose data; the latter is a Failover, which means that the primary database cannot continue to provide services, which m ...

1 software environment Oracle Linux 6.9 Oracle Enterprise Manager Cloud Control 12.1.0.4 Oracle 11.2.0.3 2 software preparation 1) Download EM database template https://www.oracle.com/enterprise-manager/downloads/cloud-control-downloads.html 2) Download Oracle Enterprise Manager Cloud Control 12.1.0.4 https://www.oracle.com/enterprise- ...

Traditional jdbc Code: package com; import java.sql.*; /** * @author liuyj * @Title: JdbcTest * @create 2020-05-27 17:31 * @ProjectName algorithm-Exercise * @Description: TODO */ public class JdbcTest { public static void main(String[] args) { Connection connection=null; PreparedStatement preparedStatement=null; ...

In MySQL, there are many powerful tools, such as mysql, mysqladmin, mysqldump, etc.1. mysql commandThe Mysql command is the most common command tool used to provide a command line interface for users to operate and manage MySQL servers.You can see how it's used in more detail through mysql --help.1) Grammar used for -e, -u, -p, -h, -P, and so ...