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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 ...

1, Core description of the project 1. Fleck is a relatively simple third-party component to implement websocket, which does not need to install additional containers. There are also several interfaces available. 2. The project is based on. net framework 4.7.2, developed on vs2019, and has not tried to run on the lower version. However, the new ...

catalog preface ES series installation Data synchronization How to search ES in. net code Single Index and multiple Index Single field search and full text retrieval Multiple conditions, time range + paging + highlighting end preface The first three series understand the installation and s ...

Each service has its own command to check the uptime of the service. But you can also use other commands for this. Source: https://linux.cn/article-12263-1.html By Magesh Maruthamuthu Translator: geekpi We all know the purpose of using the uptime command in Linux. It is used for checking Linux system uptime And the time s ...

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 { ...

Build microservice framework (database persistence layer spring datajpa) Used to Mybatis, this time for a change, integrate spring datajpa in SQuid. Source address: Build microservice framework (database persistence layer spring datajpa) Github address: SQuid introduce I've heard of HibernateJPA before, but I've never used it. Mybatis i ...

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 user portrait scenario, many tags are usually developed. As a qualifier, each tag needs to be offline after some tags are no longer in use. However, the delete related api provided by hbase can only be used for a single line. It is not easy to clean up all the data of a qualifier. Here we provide an implementation scheme based on coproce ...

In the user portrait scenario, many tags are usually developed. As a qualifier, each tag needs to be offline after some tags are no longer in use. However, the delete related api provided by hbase can only be used for a single line. It is not easy to clean up all the data of a qualifier. Here we provide an implementation scheme based on coproce ...