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The table.sql file used for testing was uploaded to my resource library... If you want to use it, you can use the following three tables for testing only. The specific contents of each table are as follows: Department table Area table Employee table There are too many specific contents. Some contents are displayed here 1. Basic quer ...

This blog is equipped with the learning video of Lao Du in station B to make learning records for later learning and review. It is not used for other purposes. Video link: https://www.bilibili.com/video/BV1Vy4y1z7EX?spm_id_from=pageDriver Chapter 1 MySQL overview 1.1 Preface DB: database, warehouse for storing dataDBMS: database managem ...

1, Foreword       golang's time.Ticker is generally used to execute tasks as a time cycle. 2, demo       This is an example posted on the official website. Its function is to output the current time every 10s. package main import ( "fmt" "time" ) func main() { ticker := time.NewTicker(time.Second) defer ...

mybatis learning notes, 2.MyBatisTest 1. Introduction 1. Interface programming Native: Dao = = = = > daoimplmybatis: Mapper ====> xxMapper.xml 2. SqlSession represents a session with the database; It must be closed after use; 3. SqlSession, like connection, is non thread safe. You should get a new object every time you use it. ...

Introduction to character sets and comparison rules Character set introduction We know that only binary data can be stored in the computer, so how to store strings? Of course, it is necessary to establish the mapping relationship between characters and binary data. To establish this relationship, at least two things should be clear: What ch ...

Dynamic sql Dynamic SQL is one of the powerful features of MyBatis. Using dynamic SQL, we can flexibly splice SQL statements according to different conditions. Common dynamic SQL tags are as follows: ifchoose(when,otherwise)trim(where,set)foreach if When < if > sql < / if > is used, if the conditions are met, the SQL will ...

This article learned from Dataware SQL tutorial SELECT & WHERE SELECT: SELECT the necessary data from the table Query: the process of matching query / query and selecting necessary data through SELECT SELECT "Field name" FROM "Table name"; WHERE: selectively extract necessary data SELECT "Field name" FROM "Table name" WHERE "condit ...

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； 1, First knowledge of SQL SQL statements can be divided into the following three categories: 1. DDL DDL (Data Definition Language) is used to create or delete databases for storing ...

Stored program Sometimes, in order to complete a common function, many statements need to be executed. It is very annoying to enter so many statements one by one in the client each time. The uncle who designed MySQL kindly provided us with something called a stored program. This so-called stored program can encapsulate some statements, and the ...

1, Grammar select Query list from Table 1 alias [connection type] join Table 2 aliases on Connection conditions [where [filter criteria] [group by [grouping] [having [filter criteria] [order by Sort list] Classification: inner connection (★): inner External connection Left outer (★): left [outer] Right outer (★): right [outer] fu ...