Recently, the little ape needs to be on the project according to the requirements of the leaders. The database needs to realize master-slave replication. The necessity and principle of master-slave replication of the database are not explained too much in this paper. Interested children's shoes can refer to some articles on the In ...
Posted by pugs1501 on Wed, 23 Feb 2022 15:01:22 +0100
Dao interface proxy
1. Introduction to agent development mode
The agent development mode 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 mapper interface (equivalent to Dao interface). Mybatis framew ...
Posted by richclever on Wed, 23 Feb 2022 12:16:51 +0100
Master-slave database theoretical knowledge
First step The master's operations on the data are recorded in the Binary log. Before each transaction updates the data, the master records these changes and writes them to the Binary log serially. After completing the log writing, the master notifies the storage engine to commit the transaction. T ...
Posted by telefiend on Wed, 23 Feb 2022 03:45:15 +0100
In the development process, it is sometimes encountered that only a part of a certain field of the database is required. Sometimes, this scenario is more convenient and faster to operate directly through the database than through code. MySQL has many string functions that can be used to deal with these requirements, such as left, right, subs ...
Posted by mchannel on Wed, 23 Feb 2022 03:29:19 +0100
10. Multi table query of mybatis
Relational database tables are divided into
* One to many
* Many to many
give an example
The ID number is one to one. A person can only have one ID number. An ID number can only belong to one person.Users and orders are one to many, and orders and users are many to one One user can place multip ...
Posted by rgermain on Wed, 23 Feb 2022 02:19:43 +0100
I ❤ Introduction to database and SQL ❤
1. SQL classification SQL can be divided into two parts: data operation language (DML) and data definition language (DDL).
⭐ Data query language (DQL)
⭐ Data Manipulation Language (DML)
Data definition language ...
Posted by lrdaramis on Tue, 22 Feb 2022 17:06:46 +0100
Previous: I'm learning database at station b (VI): regular expressions in DQL
1, Multi table relation It can be summarized as: one to one, one to many / many to one relationship, many to many
1. One to one relationship Example: one ID card can only correspond to one person be careful: (1) Add a unique foreign key in any table to point to the ...
Posted by dolcezza on Tue, 22 Feb 2022 11:22:46 +0100
1: Check whether mysql has been installed locally
rpm -qa | grep mysql
2: Uninstall previous mysql
rpm -e Existing MySQL full name
Step 2: unzip the file
[root@MiWiFi-R3-srv ~]# tar -zxvf mysql-5.7.17-linux-glibc2.5-x86_64.tar.gz -C /usr/local/
Change the file name to mysql:
[root@MiWiFi-R3-srv local]# mv mysql-5.7.17-linux-glibc2.5-x86_ ...
Posted by otuatail on Tue, 22 Feb 2022 06:32:31 +0100
Session variable: the session variable is initialized by MYSQL every time a new connection is established. MYSQL will copy the values of all current global variables. As a session variable. (that is, if the values of session variables and global variables have not been changed manually after the session is established, the values of all these v ...
Posted by signs on Tue, 22 Feb 2022 04:19:53 +0100