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2021SC@SDUSC summary After analyzing the contents related to buffer pool in the previous blog, let's analyze the contents related to postgreSQL shared memory, which involves IPC (inter process communication). Because the process is the smallest unit of resources allocated by the operating system, each process has its own independent se ...

This note is the learning content of Alibaba cloud Tianchi Longzhu plan SQL training camp. The link is: https://tianchi.aliyun.com/specials/promotion/aicampsql； Summary of learning points: 1. Addition and subtraction of tables union, except 2. Connect the join Learning content: 1. Table addition union: SELECT product_id, product_nam ...

Create Keystone database Create the Keystone database on the MariaDB of the controller: mysql -uroot -p123456 # -u root specifies that the user logging in to mariaDB is root #-P123456 the password for the root user to log in to maraiDB is "123456" Create Keystone database: CREATE DATABASE keystone; Create keystone database ...

Learning notes on common database operations 1, How to create a new table Here is a table for creating user2: CREATE TABLE if NOT EXISTS user2( username VARCHAR(50) not NULL, password VARCHAR(50) NOT NULL, realname VARCHAR(50), phone VARCHAR(50), userid int AUTO_INCREMENT, PRIMARY key(userid) )ENGINE=InnoDB DEFAULT CHARSET=utf8; Ins ...

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 ...

The full name of WAL is Write Ahead Logging (pre write log) is a mechanism used to implement atomic transactions in many databases. It is an efficient log algorithm in databases. From the database principle, it implements the redo log mode. That is, when modifying the database, it does not directly modify the database content, but writes th ...

1, Introduction In the previous article[ springboot: those pits that use asynchronous annotation @ Async >The incorrect usage of using @ Async annotation to obtain task execution results is introduced in. Today, let's share another common error. 2, Code demonstration Here is the code of my controller, package com.atssg.controller; impor ...

Lua scripts quick start Lua is case sensitive premise After Lua is installed on this machine, the installation steps of lua can be completed Basics notes -- This is a single line comment -- [[ This is a multiline comment This is a multiline comment -- ]] Reserved keywords Reserved keyword document address variable Type when ...

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 ...