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@ Relational algebra 1. Union (U) 1.1 definition: Union (\ (\ cup \) The result of this operation, R  S, is a relationship that contains all tuples in R or S or both. Duplicate tuples do not appear in the output. Formally: \ (R\) \(\cup\) \(S\) \(=\) \(\{\) \(t | t\) \(\in\) R or t \(\in\) S \ (\} \) Joint compatibility: let R and S be two rel ...

Introduction: SQL optimization is the most important part of database performance optimization. The key of SQL optimization is inseparable from three points: table connection mode, access path and execution order. This paper focuses on several common connection modes. For multi table Association query, the execution steps of the query optimize ...

prefaceRecently, I was studying and learning the source code of leveldb and tried to rewrite leveldb RS with Rust. The memdb module in leveldb uses skiplist as a kv memory storage. The implementation of the relevant code is very beautiful, so I have this article. Leveldb implements skiplist by using Arena mode. In short, it uses linear arrays t ...

Redis OM Redis OM is an Object Mapping framework officially launched by redis, that is, Object Mapping. It allows developers to operate redis data more simply and conveniently. The data stored in redis is abstracted as Object Mapping and supports object-based redis data persistence and streaming query operations. Currently, only four developm ...

CRUD insert insert should mainly focus on the processing of primary key fields by mybatis plus Primary key generation strategy Extension: common strategies for generating primary keys UUIDSelf increment IDSnowflake algorithmGenerated using redis Snowflake algorithm: The id generated by SnowFlake algorithm is a 64bit integer, which ...

Redis overview Redis is a key value storage system (official website: http://redis.io ), is a distributed cache database Redis initial operation Start redis service Startup in docker environment (multiple containers need to be run to start docker environment): The # bottom layer of docker start redis01 is also started through redis serv ...

1. Four characteristics of transactions A transaction is an integral unit of one or more SQL statements. A set of SQL statements in a transaction either succeed or fail. Four properties ACID Atomic atomic consistency Isolation for concurrency in the database, the better the isolation, the lower the concurrency. It is based on innodb's locki ...

The focus of this article is to teach you how to operate MySQL database with Python. 1. General steps In fact, there is a general step here, which is written dead. Just follow it. # 1. Import related libraries import pymysql # 2. Link MySQL server db = pymysql.connect(host='localhost' , user='root' , password='******' , port=3306 ,db='sp ...

The original content of GreatSQL community cannot be used without authorization. Please contact Xiaobian and indicate the source for reprint.In the near future, we plan to create a docker image of GreatSQL to facilitate community users to use GreatSQL.The environment for making docker images is based on CentOS 7.9:[root@greatsql]# cat /etc/redh ...

catalogue 1, Installation environment 2, Initialize database 3, Configure master node masterdb 4, Configure slave node slavedb 5, Validate database master-slave service 1, Installation environment preparation 1. Node planning Prepare two virtual hosts to act as master dB and slave DB respectively IP addressHost namenode192.168.18.8mas ...