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Original Link: https://zzzzbw.cn/article/18 Recent concurrency problems have been encountered in the company's business, and it is still a very common concurrency problem. The company's business is the most common "order + account" problem, which is considered a low-level error. Since the company's business is relatively complex an ...

Write in front: follow Master Kang of station B to learn the notes summary and self summary of mysql. 1. Create storage function Syntax format: CREATE FUNCTION Function name(Parameter name parameter type,...) RETURNS return type BEGIN Function body #There must be a RETURN statement in the function body END explain: Parameter li ...

Usage scenario: when the amount of data fetched reaches a certain level, paging is required for data segmentation. When we do not use the paging function, we will face many problems: Problems with the client: if too much data is displayed on the same page, the user experience will be seriously affected because the page is too long, it is ...

I Several cases of index failure The index does not always take effect. For example, the following situations will lead to index invalidation If there is or in the condition, it will not be used even if some of the conditions are indexed (this is why or is used as little as possible) (user_id is not indexed) Note: to use or and make the index ...

Mybatis 1. Introduction MyBatis was originally a part of apache Open source project iBatis, 2010 project Migrated from apache software foundation to [Google Code]( https://baike.baidu.com/item/google Code / 2346604) and renamed MyBatis. Moved to in November 2013 Github. iBATIS comes from the combination of "internet" and "aba ...

4.3 data definition 4.3. 1 Definition and deletion of mode What is a database schema? Database schema is a logical grouping object. Database schema is a collection of database objects, which contains various tables, views, stored procedures, indexes, etc. Imagine a schema as a container for objects. Database schema can be used as a namespace ...

1. Concept of database DB: database: a "warehouse" for storing data. It holds a series of organized data;DBMS: Database Management System. Database is a container created and operated by DBMS;SQL: Structure Query Language: a language specially used to communicate with the database;Relationship diagram of the three: 2. Common ...

Due to the learning needs, I will start to learn the basic knowledge of database and the preparation and use of SQL statements from today. Therefore, I record my learning process here to urge myself, consolidate the knowledge I have learned, and hope to help more introductory students. 1. Establish database create database db_name;//db_name i ...

1. No '' after variable conversion 1.1. Create a stored procedure, which contains a cursor to query the table in a certain mode. It also contains a print of the for loop. The print is added to make the effect of dynamic statements substituted with parameters more intuitive. CREATE OR REPLACE PROCEDURE T_1208(COL VARCHAR(100)) AS CURSOR T_CS ...

Introduction to MyBatis MyBatis is an excellent persistence layer framework that supports customized SQL, stored procedures, and advanced mapping. MyBatis avoids almost all JDBC code and manually setting parameters and getting result sets. MyBatis can use simple XML or annotations for configuration and original mapping, and map the inte ...