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The world.sql exercise on the mysql official website is used DQL introduction select show Application of select statement select is used alone select @@port; --View port select @@basedir; --View the directory where the program is located select @@server_id; --see server_id mysql> select database(); --View the current library +- ...

Innodb of Innodb engine_ lock_ wait_ Timeout parameter description explain First, the Innodb engine will lock the corresponding row when executing the update statement and will not release it until the transaction is committed or rolled back. In the process of holding a row lock, if other transactions b also want to modify the data of the loc ...

MyBatis connects to Mysql to complete addition, deletion, modification and query 1. Step 1: create a SpringBoot project Select related dependencies Note: if you forget to import the related dependencies: you can import them manually. Search the name of the related jar in the link below maven warehouse Step 2: create database tables accordin ...

php+mysql to achieve a simple library management system ps: the front-end page design is a little ugly. I'll make do with it. Ha ha ha. It does not have user and administrator functions. If you want to realize it, you only need to selectively use the function of the home page according to the account information in the database. Database relat ...

1, The table structure in the existing database casemanage is shown in the following figure TABLENAME:afinfo Idnameagebirthsexmemo1Xu Hongguo371979-03-23malehigh school2Wang Fangfang261988-02-06femaleundergraduate3Xu Xiaosheng241990-04-02malemaster4Chen Xiao301984-09-12femaledoctor5Zheng Kai271987-12-30malejunior college 1) Please write s ...

Hello, everyone. I'm Mr. Tony, who only talks about technology and doesn't cut his hair. Today, we introduce an application CASE of CASE conditional expression, using the example table Click here to download. If the company is about to celebrate its 20th anniversary, it plans to distribute an anniversary gift to all employees. The rules for ...

1. Vue advanced usage 1.1. Custom components After learning the Element component, we will find that the component is actually a custom label. For example, the encapsulation of. In essence, a component is a reusable Vue instance with a name, which can be defined by ourselves. Define format Vue.component(Component name, { props:Prope ...

1, Mybatis annotation development single table operation 1.1 common notes of mybatis In recent years, annotation development has become more and more popular. Mybatis can also use annotation development, so that we can reduce the writing of Mapper Mapping file. We first learn about some basic CRUD, and then learn about complex mapping ...

Database advanced After learning database related knowledge, please be sure to see the precautions. Precautions for database statements: https://blog.csdn.net/qq_43098690/article/details/121661835 1, Database integrity As the name suggests, the data stored in the database must be valid, that is, validity and accuracy. Ensure data int ...

Welcome to the MySQL technical articles shared by the great SQL community. If you have any questions or want to learn, you can leave a message in the comment area below. After seeing it, you will answer itproblemRun the following Python code, but you can't always update the data:import pymysql conn=pymysql.connect( host = '127.0.0.1', user = 'y ...