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Project scenario: Spring boot project write off card secret recharge in concurrent test, a card secret is successfully recharged repeatedly Problem Description: The first time I wrote, I didn't consider so much, so I added several logic to verify the card secret status in the business layer. As long as the card secret status is OK, I can ...

1. Single table query 4.1 basic query statement Query the contents of the field Name and Salary; Query the contents of the whole table. USE Company; #Please add the implementation code here ########## Begin ########## ########## retrieving the Name and Salary ########## select Name,Salary FROM tb_emp; ########## retrieving all the tab ...

Analysis of JDBC core technology Database connection pool 1. Necessity of JDBC database connection pool When developing web programs based on database, the traditional mode basically follows the following steps: Establish database connection in the main program (such as servlet and beans)Perform sql operationsDisconnect database Pro ...

A simple instance of JDBC connecting to MySQL has been written before, which can only be understood as simple. Some of these processes can be reused, such as loading drivers, establishing connections, releasing resources, etc. in order to improve the reusability of the code, we need to standardize the overall framework of the project. The fol ...

Collation of common sql statements In mysql, common sql statements are: Change Password: alter user 'root'@'localhost' identified with mysql_native_password BY 'New password'; alter user 'root'@'localhost' identified with mysql_native_password BY '123456'; DDL (Data Definition Language): Data Definition Language, which is used to define dat ...

1. Introduction to SQL SQL is a structured query language. It is a set of operation commands specially established for database. It is a database language. The interactive operation of the database is inseparable from SQL, which provides great convenience for us to manage the database. 1.1 database use case construction Note: all of ...

The CAS operation process mentioned above is not very difficult. But the above description is not enough. Next, I will introduce some other background knowledge. With these background knowledge, we can better understand the follow-up content. 2. Background introduction As we all know, CPU transmits data through bus and memory. In the multi- ...

First, let's introduce my What's the use of ini folder: my Ini is the configuration file used in the MySQL database. This configuration file will be read when the MySQL server starts. We can update the configuration by modifying this file. my. If the INI file does not exist, you can first look at my Is the INI file hidden under the ProgramData ...

1. Database engine 1.1 INNODB AND MYISAM MYISAMINNODBTransaction supportI won't support itsupportData row lockingI won't support itsupportForeign keyI won't support itsupportFull text indexsupportNot supported (full text retrieval is supported in InnoDB version 1.2. X)Table space sizelessLarger, about 2 times General operation: MYISAM: space ...

background Recently, many people have encountered mysql exception problems. They checked them one by one. But today, I suddenly encountered this problem myself. I usually follow the problem to find Du Niang. However, in order to have a faster solution, I decided to take this opportunity to sort out the solutions for mysql exceptions. The mysq ...