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preface We all know what transactions are, and Spring transactions use AOP to provide declarative and programmatic transactions on the database to help us simplify development and decouple business logic and system logic. But what is the principle of Spring transactions? How do transactions propagate between methods? Why do transactions fail s ...

varchar(N), N refers to the maximum number of characters, not bytes. Remember: (1) MySQL requires that the definition length of a row cannot exceed 65535. (2) If a single field is greater than 65535, it is converted to TEXT. (3) The maximum limit for a single line is 65535, excluding TEXT and BLOB. (4)utf8: 1 character = 3 bytes, 1 Chinese ...

Data segmentation can be divided into two ways according to its segmentation type: vertical (vertical) segmentation and horizontal (horizontal) segmentation 1.ShardingSphere-Jdbc Shardingsphere Jdbc is positioned as a lightweight Java framework and provides additional services in the Jdbc layer of Java. It uses the client to connect directly ...

Introduction: This article is translated from Altinity's series of technical articles on ClickHouse. ClickHouse, an open source analysis engine for online analytical processing (OLAP), is widely used by companies at home and abroad because of its excellent query performance, PB level data scale and simple architecture. This series of technical ...

Redis client summary redis is a distributed cache database with C/S architecture. It has its own command-line client and corresponding Java or other language clients. redis can be read and written through some API s in these clients. preparation Step 1: create a project. Create a maven parent project, such as 03 redis, and create two sub p ...

1. Introduction to redis transaction 1.1 general Transaction is a business and can also be regarded as a logical work unit. It is a control mechanism introduced to ensure the integrity of business and the correctness of data. In principle, transactions must meet the four characteristics of ACID (atomicity, consistency, isolation and persisten ...

Introduction: NoSql, non relational database; Single thread + multiplex IO multiplexing technology Atomicity of Redis Because redis is single threaded, the execution of all single commands is atomic Applicable scenarios: Highly concurrent reading and writing of dataMassive data reading and writingFor high data scalability Key points: redis ...

We all know that in MySQL, MyISAM is faster than InnoDB query, but many people don't know the principle. Today, let's talk about the principle and verify whether MyISAM is really faster than InnoDB. Before exploring the principle, let's verify the query speed. verification Let's verify two questions: 1. Is MyISAM faster than InnoDB query t ...

1 Introduction 1.1 background In our current project architecture, the Web server (Tomcat) and database are basically deployed independently and monopolize the server resources. With the growth of the number of users, concurrent reading and writing to the database will increase the pressure on database access and lead to performance degradati ...

1, Simple search 1. Fuzzy condition query For search function Example: find out which names contain the letter e select *from emp where ename like '%e%'; Exercise: query the employees whose names end with e select *from emp where ename like '%e'; Query the employee whose last character in the name is e select *from emp where ename li ...