Programming VIP

1, Introduction Why constraints Data Integrity refers to the Accuracy and Reliability of data. It is proposed to prevent the existence of data that does not comply with the semantic provisions in the database and to prevent invalid operation or error information caused by the input and output of error information. Entity Integrity: ...

1. Multi table query: 1. Query syntax: select Column name list from Table name list where.... 2. Prepare sql Create department table CREATE TABLE dept( id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20) ); INSERT INTO dept (NAME) VALUES ('Development Department'),('Marketing Department'),('Finance Department'); Create employee tabl ...

multi-table queryMulti table query, also known as association query, refers to two or more tables completing the query operation together.Prerequisite: these tables queried together are related (one to one, one to many). There must be an associated field between them. This associated field may or may not have a foreign key. For example: employe ...

DML language Data operation language: Inserting: insert ing Modify: update Delete: delete 1, Insert statement Mode 1: Syntax: insert into table name (column name...) Values (value 1,...); Features: it supports inserting multiple rows and querying subsets SELECT * FROM beauty; 1. The type of the inserted value should be consistent or com ...

1. Preface As we all know, Python's most popular crawler framework is Scrapy, which is mainly used to crawl website structural data Today, we recommend a simpler, lightweight and powerful crawler framework: feapder Project address: https://github.com/Boris-code/feapder 2. Introduction and installation Similar to Scrapy, feapder supports l ...

MySQL [Delete error] uses binlog to quickly roll back (python script is not required) Locate binlog position according to misoperation time In specific usage scenarios, binlog may store hundreds of thousands or more pieces of data, and the amount of data reaches the size of G. therefore, determining the location of binlog needs to be filtered ...

brief introduction This article summarizes and briefly introduces the logs in mysql, which will not be involved too deeply. The main purpose is to have a systematic understanding of the log files in MySQL. Each log file will be specifically analyzed and summarized later. Log classification Log files in MySQL include configuration files, erro ...

brief introduction This article summarizes and briefly introduces the logs in mysql, which will not be involved too deeply. The main purpose is to have a systematic understanding of the log files in MySQL. Each log file will be specifically analyzed and summarized later. Log classification Log files in MySQL include configuration files, error ...

Signal generation Concept of signal Signaling is a way of asynchronous notification of events between processes, which belongs to soft interrupt Generation method: Generate a signal to the process through the terminal keyboard. If the process can terminate the program by pressing "ctrl + c" when running, it is actually sending ...

Tip: after the article is written, the directory can be generated automatically. Please refer to the help document on the right for how to generate it @TOC Preface (MySQL version 8.0.28) Recently, I studied mysql master-slave construction and read many tutorials. They all create mysql master and slave in the docker container, but my own ma ...