Programming VIP

This note is the learning content of Alibaba cloud Tianchi Longzhu program SQL training camp. The link is: https://tianchi.aliyun.com/specials/promotion/aicampsql Exercise 1 Please use the quarterly revenue forecast data sets "Income Statement.xls", "Company Operating.xlsx" and "Market Data.xlsx" of A-share liste ...

1, Connection query Classification according to the way of table connection: Internal connection: equivalent connection, non equivalent connection and self connection External connection: left external connection (left connection), right external connection (right connection) Syntax: join ... on ... select ... from Table name 1 join Table na ...

1. DQL operation sheet 1.1 create database and copy tables Create a new db2 database CREATE DATABASE db2 CHARACTER SET utf8; Copy the emp table in the db1 database to the current db2 database 1.2 sorting The sorting effect of the query can only be displayed through the order clause, and the sorting effect will not be displayed thro ...

Referring to owasp, this paper focuses on providing clear, simple and operable guidance to prevent SQL injection vulnerabilities in applications. Unfortunately, SQL injection attacks are common due to two factors: Significant prevalence of SQL injection vulnerabilities The attractiveness of the target (i.e. the database usually contains all ...

0. Case environment 0.1 case data initialization sql CREATE DATABASE /*!32312 IF NOT EXISTS*/`mybatis_db` /*!40100 DEFAULT CHARACTER SET utf8 */; USE `mybatis_db`; DROP TABLE IF EXISTS `orders`; CREATE TABLE `orders` ( `id` int(11) NOT NULL AUTO_INCREMENT, `createtime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMEST ...

1, The maximum number of visits per user in a single month as of the end of each month and the total number of visits accumulated to that month 1. Create table CREATE TABLE IF NOT EXISTS visits( userid VARCHAR(10), datetime1 DATETIME, visits INT)ENGINE=InnoDB DEFAULT CHARSET=utf8; 2. Insert data INSERT INTO visits VALUES('A','2021-01-03 14 ...

catalogue introduce background So we need to be more complicated Points of interest A QA question needs "last week's data", which makes me think. Using the DATEADD function with a "WW" interval is easy, but it subtracts 7 days from today. This is different from "last week", because "last week" sta ...

In the later operation and maintenance of MySQL database, DBAs sometimes encounter such a phenomenon: when troubleshooting the problem, they find that the active and standby MySQL has been switched, and it is normal to check the MySQL service. DBAs have not done the switching operation, and the server has not been maintained. Fortunately, the b ...

Links 1. Database design of student achievement management system - MySQL Database design of student achievement management system - MySQL 2. Medical information management system database – MySQL Medical information management system database – MySQL 3. Mail management database design – MySQL Mail management databas ...

I Aggregate query Aggregate functionmeaningcount()Calculate the number of records (rows) in the tablesum()Calculate the total value of the values in the value column in the tableavg()Calculate the average of the data in the value column in the tablemax()Find the maximum value of data in any column in the tablemin()Find the minimum value of d ...