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Summary of Myqsl knowledge points 1, Database related concepts DB: a database that holds a set of organized data containersDBMS: database management system, also known as database software (product), is used to manage data in DBsql structured query language is a language used to communicate with DBS 2, mysql common commands 1. View all curr ...

🔎 MySQL notes Retrieve data Retrieve different rows select distinct vend_id from products Limit the result, that is, limit the number of rows output select prod_name from products LIMIT 4,5 //Indicates that five rows of data are retrieved from the fourth row. The first is the starting position and the second is the number of rows to be r ...

Baidu cloud disk: link: https://pan.baidu.com/s/1PyR_UiaKZetXlAuJ7KwYUw   Extraction code: 0601 Package preparation   -rw-r--r-- 1 root root 729891578 12 February 18:25 mysql-5.7.34-el7-x86_64.tar.gz Let's first check whether mariadb (centos) is installed on the system. If so, uninstall it [root@master module]# rpm -qa |grep mari ...

typora-copy-images-to: img 1, Dao interface proxy implementation 1.1 introduction to agent development mode The agent development method of Mybatis is adopted to realize the development of DAO layer, which is the mainstream of entering the enterprise later. Mapper interface development method only requires programmers to write map ...

MySql single table & constraint & Transaction 1. DQL operation sheet 1.1 create database and copy tables 1) Create a new db2 database CREATE DATABASE db2 CHARACTER SET utf8; 2) Copy the emp table from the db1 database to the current db2 database 1.2 sorting Through the ORDER BY clause, you can sort the query results (sorting is onl ...

Phase 2 ------------------------------------------------------------------------------- database What is a database? In short, it is a warehouse for storing and managing data. Common databases are divided into: Relational database, Oracle, MySQL, SQLServer, Access non relational database, MongoDB, Redis, Solr, ElasticSearch, Hive, HBase My ...

preface: Followed by the previous article. The above analyzes the whole process of the consumer sending the request, and finally sends the request to the Provider through NettyChannel. Of course, a series of processing has been carried out in the middle. From the perspective of Provider, this paper discusses how the service Provider handles t ...

preface I'm sure you've heard that if the character codes of the two tables are inconsistent, the index field will cause index invalidation during join, but is that true? This article will carefully analyze this problem. prepare We first prepare two tables, one using utf8 character set and one using utf8mb4 character set, and insert a piece ...

1, Introduction MySQL currently has the following index types: 1. General index 2. Unique index 3. Primary key index 4. Composite index 5. Full text index 2, Statement CREATE TABLE table_name[col_name data type] [unique|fulltext][index|key][index_name](col_name[length])[asc|desc] unique|fulltext is an optional parameter, which represents a un ...

First, execute the following sql statement to generate the data required for the test to facilitate the verification of index failure. create table table_test( id int(4) primary key auto_increment, c1 char(10) not null, c2 char(10) not null, c3 char(10) not null, c4 int(4) not null ); insert into table_test(c1, c2, c3, c4) values ('11one', ...