python data analysis - use of MYSQL variables
1, Variable introduction
1. MYSQL variables can be divided into two categories: system variables and user variables (also known as user-defined variables). 2. System variables are divided into global variables and session variables. User variables are divided into local variables and user variables. 3. Scope: that is, the effective range, when ...
Posted by itbegary on Thu, 31 Mar 2022 19:00:44 +0300
node connection MongoDB and common operation records
Personal interface for the back end of the whole stack project
preparation
I think it is necessary to understand some concepts in advance
Install mongoDB Library
npm i mongodb
Install a mongodb Library
Connect database
// If the database address is not changed, it is the default address
const url = "mongodb://localhost:27017";
...
Posted by goodrunb on Thu, 31 Mar 2022 11:06:18 +0300
Syntax, engine, transaction, optimization, index, user management, backup, design protocol and JDBC connection pool of MySql basic overall textbook
MySql
Java EE: enterprise development, Web oriented
Front page: display dataBackground: connection point, link frontDatabase: save data
Database should learn operating system, data structure and algorithm, discrete data, mathematical circuit, architecture, compilation principle and practical experience well
Why: learn everything beca ...
Posted by HektoR on Thu, 31 Mar 2022 09:45:26 +0300
MySql notes-03 data manipulation language (DML)
Data manipulation language (DML)
1. Concept
Data manipulation language (DML), through which users can realize basic operations on the database. For example, query, insert, delete and modify the data in the table. However, there are three main forms of DML: data insertion, modification and deletion
2. Insert data
Insert statement ...
Posted by Gomesh on Thu, 31 Mar 2022 00:08:34 +0300
Design and implementation of online furniture mall platform based on Java Web + springboot (java+springboot+mysql+ssm)
Design and implementation of online furniture mall platform based on Java Web + springboot (java+springboot+mysql+ssm)
Main technologies: springmvc, springboot, mybatis, mysql, jQuery, layui and other technologies Specific functional modules:
(1) User registration and login functions:
① User registration function: visitors to the website reg ...
Posted by markts on Wed, 30 Mar 2022 18:49:38 +0300
MySQL 8 builds MHA with one master and two slaves
1, Introduction
MHA (Master High Availability) is a MySQL high availability solution. It is a management tool developed in perl language. It polls and detects the availability of MySQL master nodes, finds faults, automatically transfers faults, selects a slave node to be promoted to a new master node, replaces the old master node and continues ...
Posted by Soogn on Tue, 29 Mar 2022 18:19:02 +0300
day 05 DQL data query language --- connection query --- enter the room
Because sql statements are not case sensitive, all commands in this article use lowercase for convenience
Previous contents
day 01 first knowledge of Mysql and DDL data definition languageday 02 DML data operation languageday 03 DQL data query language -- a first glimpseday 04 DQL data query language - single table query - a slight succ ...
Posted by kampbell411 on Tue, 29 Mar 2022 07:33:25 +0300
Shandong University Project Training - map circle system - APP
Basic configuration settings and partial database creation
1, Basic configuration settings
About the basic configuration, it is mainly about solving cross domain problems and connecting to the database.
1. Solve cross domain problems
The IP address and port number of the front-end wechat applet and App are different from those of the Spring ...
Posted by bull on Sun, 27 Mar 2022 19:10:53 +0300
mysql stored procedure
MySQL stored procedure0. Environmental description:Softwareeditionmysql5.6HeidiSQL 1. InstructionsStored procedure is an important object of the database. It can encapsulate the set of SQL statements, can be used to complete some complex business logic, and can input and output parameters (similar to the writing of methods in java).When creatin ...
Posted by poisa on Sat, 26 Mar 2022 18:42:07 +0300
Detailed and complete knowledge of sql statements
Modify database table
Modify table name:
alter table Old table name rename as New table name
Add table fields
alter table Table name add Field column properties
For example: alter table student age int(11)
Modify the fields of the table
Modify constraints
alter table Table name modify Field column properties[];
For example: ...
Posted by jyushinx on Sat, 26 Mar 2022 12:26:12 +0300